"Simon" has been sold out at Toys R Us for more than a month.

Korvettes is giving rain checks for "Speak & Spell" but isn't promising to redeem them before Christmas.

Mattel's "Electronic Football" ought to be back in stock at Woodward & Lothrop today, but toy buyer Adrian Borsetti fears it will be gone again by next week.

As frustrated parents hunting through store after store are learning, the electronic games that are on almost every kid's Christmas shopping list this year are getting harder and harder to find.

Despite price tags running from $20 to $60, high-tech toys are selling faster than Santa's elves can build them.

Toy makers blame the shortages on the companies that produce the thumbnail-sized microcomputers known as "chips." Inside every electronic toy is a heart of silicon, a $5 genius that flashes the lights, spells the word or sacks the quarterback whenever a 12-year-old pushes the right button.

The chip makers -- chiefly Texas Instruments -- say they can't chomp them out fast enough to keep up with the runaway demand that has turned electronic toys into a $500 million business in just three seasons.

The chip shortage is so severe that even Texas Instruments' own best-seller, the Speak & Spell talking textbook, is hard to come by. One father tried half a dozen Washington discount outlets before shelling out the $60 list price at Bloomingdales.

Department stores may be the best source for the hardest-to-find toys because the cut-rate toy supermarkets usually sell out first.

High prices are discouraging few purchasers, the stores report. "The cost is astronomical, but people are buying them," said a spokesman for Toys R Us, the biggest toy chain in the nation. "Cost doesn't seem to be a factor, no matter how bad the economy is."

The season's most-wanted items -- and the toughest toys to find -- include:

Coleco's "Head-to-Head Football", a two-player game that outscores Mattel's "Electronic Football" in the Christmas best-seller bowl. The football games are the most popular of a series of silicon-smart sports toys made by the two companies.

"Merlin", a Parker Brothers game that looks like a Princess Phone and plays six games ranging from tic-tac-toe to blackjack and plays music to boot.

"Simon" a $40 "entertainment unit" shaped like a flying saucer that challenges players to follow its flashing lights.Milton Bradley Co. figures on selling 1.5 million Simons this season, and competitors are cashing in with similar toys like Castle's "Einstein" and Tiger's aptly named "Copy Cat."

"Simon" isn't the only electronic toy that's been cloned by a rival toy maker. Toys and games are almost impossible to patent, and even the most exclusive stores are selling "knockoffs" because the originals are in such short supply.

"The moment that we saw that certain suppliers were not going to be forthcoming, we hurriedly filled in from other resources," said Ian McDermott, chief toy buyer for F.A.O. Schwarz, the three-story toy store on New York's Fifth Avenue.

"We're faced with American companies who have spent millions on TV ads preselling these new and established games, and they're feeding them to us like babies because of the shortage of chips," McDermott added. "It's a constant battle. We're helpless. There's just not enough to go around."

Woodies toy buyer Borsetti said suppliers like Mattel are allocating their scarce items based on the amount of business stores do with the company. The more Mattel toys a store buys, the more "Electronic Football" games it gets.

"Business is phenomenal," he added, and customers who don't find the specific microprocessor whiz-bang they want usually buy some other electronic gee-gaw.

"It started out with 'Star Wars'," said Bosetti. Electronic games "stepped the children into a whole new area. Rather than just a toy, this is more like a computer. It's not just something they play with, it's a game that can beat them."

He estimates electronic games will bring in 25 percent of Woodies' toy business this season, and Milton Bradley projects electronics will account for 45 percent of its game volume this Christmas, up from 38 percent last year, 18 percent in 1977 and zero the year before.

The advent of electronics is dramatically changing the toy business. Tic-tac-toe players will never go back to paper and pencil after they've played against "Merlin"; the days of the ordinary board game may be over when semiconductor brain teasers like "Stop Thief" and "Electronic Detective" nab the kids who used to play "Clue."

Board games rarely sell for more than $12 -- less than the cheapest electronic marvel -- and computerized toys are likely to get more exepensive as they grow more sophisticated. "You put a $5 chip into a game, and suddenly you've got a very expensive game," said Michael Moone, vice president and general manager of the game division of Milton Bradley.

"Any one of these games is upwards of $1 million in R&D (research and development) compared with $75,000 for a board game," said the man whose company makes "Simon."

The toy makers say that the micorprocessor chips found in such games as "Scrabble Sensor" or Ideal's "Maniac" are just as advanced as those used in on-board computers that control auto exhaust emissions. In fact, car makers' orders for the same chips have siphoned supplies away from the toy companies, according to Mattel's Jack Fox.

"Our function is to figure out a way to make them (the games) so people can afford them," Fox said. "Part of engineering is cost engineering."

With electronic games, a new group of consumers is now being sought after by the toy manufacturers. "We've penetrated the 15 to 35 age market, which has a substantial amount of discretionary income," said Michael Moone.

Also, traditional toy and game-buying patterns are changing. Although most toys are bought at Christmas as gifts, Milton Bradley found that 60 percent of the electronic game buyers were getting it for themselves.

"It's providing more year-round merchandising in what has been a very seasonal industry," said Schwarz' McDermott. Mothers do most toy buying, but "males seem to be more involved in both the purchasing of and the playing with electronic toys and games," says a market study by NPD Research Inc. The study found the average electronic game sold for $18, more than four times the $4 price of the average toy.

Games will grow more expensive and more sophisticated as toy makers exploit the electronic-chip technology. "What we have right now is just the tip of the iceberg," said Barbara Wruck of Coleco.