Prince and Princess Michael of Kent are in town for a "private" visit until tomorrow, according to a spokesman at the British Embassy, and are staying at the residence of British Ambassador Sir Oliver and Lady Marjory Wright. Yesterday they walked seemingly unnoticed through the National Gallery, visiting the "Treasure Houses of Britain" exhibit and then lunching upstairs with John Wilmerding, deputy director of the gallery. Afterward, the royal couple went off to shop in Georgetown. Bardot Seeking Another Husband

French actress Brigitte Bardot, who retired from the screen in 1973, wants to marry again, for the fourth and final time. Admitting that she was lonely, she told the weekly Paris magazine Figaro that she is looking for a man who is "intelligent, kind, understanding, a bit wild and fun."

Bardot, who was once told by the late president Charles de Gaulle that she was a bigger moneymaker for France than the Renault automobile firm, is no longer such a valuable commodity. She complained in the interview that recently a clerk in the town hall of the Riviera resort of Saint-Tropez, where she has lived for the past 20 years, insisted on her producing an official document proving that she really was Brigitte Bardot.

Bardot, 51, has been married to film director Roger Vadim, French actor Jacques Charrier and West German playboy Gunther Sachs. She has a son from her marriage with Charrier. She is currently writing her memoirs and spends most of her time as an advocate for animal rights. The Super Bowl at Sea

Here's progress for seafaring sports fans: For the first time a ship at sea will broadcast the Super Bowl game on Sunday. Comsat will televise the game to the Queen Elizabeth 2, traveling in the Pacific Ocean about 100 miles off the coast of Peru. It won't be a live broadcast, however. The game will be played at dinner time, so the program will be taped and viewed later in the evening.

Sending regular TV pictures by satellite to ships at sea is something new, and the Super Bowl transmission is part of an experiment to see if TV shows can routinely be relayed to ships and oil-drilling platforms. The transmission will be bounced off three satellites before being beamed down to a dish about seven feet across on board the QE2. End Notes

The National Gallery of Art in London announced yesterday it has chosen American architect Robert Venturi to design a long-delayed extension to its neoclassical building on London's Trafalgar Square. The gallery has made four attempts since 1980 to build an extension on a site at the square's northwest corner, left empty since a bomb fell there during World War II. Venturi's plans for the extension are still under development and will not be released for another year, gallery officials said . . .

Moviemaker Steven Spielberg and Universal Studios were sued for $20 million yesterday by a French author who claims her book was the basis for the hit film "E.T." Yvette de Roils de Fonchane claims in her federal court suit filed in Los Angeles that she wrote her book, "Child of the Stars," in 1979, and Spielberg infringed on her copyright in his 1982 film. Spielberg could not be reached for comment . . .

Irv Kupcinet, host of the longest running talk show in television history, will take his final bow today with his last "Kup's Show." Kupcinet, 73, taped his final show at public television station WTTW in Chicago yesterday. The show, originally called "At Random," premiered on Chicago television in 1959 . . .

Robert Latta, the Denver meter reader whose uninvited stroll through the White House on Inauguration Day last year embarrassed the Secret Service, has written a book about "what really happened." Latta, 44, said he wrote the book, titled "Meter Reader Goes to the White House -- The Truth and Not the Truth," to help recoup the $9,000 he spent on travel, legal fees and bond. He said the case depleted his 80-year-thur Bartow literary payday does not appear to be forthcoming, however: Latta said he has written 50 literary agents about the book, but only one showed interest.