How about a "Zbig-and-Bud show" to drum up support for President Reagan's quest for aid to the contras? According to a source close to the Friends of the Democratic Center in Central America (Prodemca), the idea of pairing former national security affairs advisers Zbigniew Brzezinski and Robert C. McFarlane in a roadshow was floated in a White House meeting with Prodemca.

Prodemca, you may recall, has aimed to foster an aura of bipartisan support for Reagan's aid request. The group, which receives funds from the National Endowment for Democracy, a federal agency, prominently displayed its backing of contra aid in full-page ads in The Washington Post and The New York Times -- signed by Brzezinski, among others.

After the House defeated the first contra aid bill, Prodemca planned a second phase of its offensive. Two weeks ago, Prodemca's leaders initiated a meeting at the White House with the president's senior political staff, including Mitch Daniels, the political director, and Patrick Buchanan, the communications director.

The Prodemca leaders, including Penn Kemble, chairman of the executive committee of the Coalition for a Democratic Majority, told the White House that they wanted help in putting together a nationwide tour of distinguished speakers on behalf of the president's position. The speakers they had in mind were McFarlane and Brzezinski, one a Reagan adviser, the other a Carter adviser. The idea was that the mere presence of the two together before mostly Democratic gatherings would create the desired image of bipartisanship.

The White House agreed to help, according to a source there. But then Prodemca's plans went awry. Prodemca couldn't sychronize the schedules of its star features. "I'm not doing it, because I'll be traveling abroad," said Brzezinski.

Prodemca also encountered difficulty lining up Democratic groups to hear their speakers, a Democratic Party official said. UP IN THE AIR FORCE . . .

As expected, President Reagan nominated Edward Aldridge yesterday to be Secretary of the Air Force. If confirmed by the Senate, Aldridge would replace Russell Rourke, who resigned Monday for personal reasons after four months in the post.

Aldridge, 57, has been serving as undersecretary of the Air Force since 1981. Previously, he was a vice president of System Planning Corp. and served in the Defense Department from 1974 to 1977. STEP RIGHT UP . . .

The U.S. Mint announced yesterday that you can get your Secretary of the Treasury James A. Baker III medal now. The 3-inch bronze medal runs $16.00 if ordered by mail.

Said the Mint's release: "Secretary Baker's medal is part of the Secretaries of the Treasury Series medals . . . . Included in the series are the official medals of Alexander Hamilton, Albert Gallatin and Andrew Mellon."

What the release doesn't say, a spokesman for the department did: Striking a medal in the secretary of the treasury's image is standard operating procedure. Also included in the series, therefore, is a medal in the image of Joseph W. Barr, who was secretary of the treasury for less than a month, from Dec. 23, 1968, through Jan. 20, 1969. TENTERHOOKS . . .

Expected top-level personnel changes at the Justice Department are likely to be delayed for several more weeks until Deputy Attorney General D. Lowell Jensen formally is nominated for a federal judgeship in northern California.

When that happens, however, the musical chairs will be set in motion. As reported last week, Justice sources say that Associate Attorney General Arnold I. Burns, a former Manhattan lawyer, will move up to the deputy's spot. Stephen S. Trott, a career prosecutor who now heads the Criminal Division, will succeed Burns in the No. 3 job. And William F. Weld, another career prosecutor who is U.S. attorney in Boston, will take Trott's place at the Criminal Division. Watch this space. NEW SET OF WHEELS . . .

"A changing concept in the transportation and delivery of mail" is how Postmaster General Albert V. Casey described the new postal van unveiled yesterday, of which the postal service has ordered 99,150. The "long-life" delivery vans, made by Grumman Corp., are designed to last for 24 years and save the Postal Service $6 billion in replacement and maintenance costs over that time. The cost of this largest vehicle purchase order in the history of the U.S. Mail is $1.1 billion.

Where does the "changing concept" part come in? The vans will carry roughly twice as much mail as their Jeep forebears and are designed to serve as containers themselves, holding smaller standardized containers, such as those in street-corner mailboxes. PRESSING ON . . .

Lance Morgan, press secretary to Sen. Daniel Patrick Moynihan (D-N.Y.) for 2 1/2 years, is leaving in a week to take a job with Burson-Marsteller, a public relations firm. No successor has been named. At his new job, he will act as press counselor to Morgan Stanley, the investment banking firm that is competing to buy the Conrail railroad freight system from the government. ALSO MOVING . . .

Also announced by the White House yesterday was the nomination of Jean McKee, executive director of the Federal Mediation and Conciliation service since 1983, as a member of the Federal Labor Relations Authority.

The authority handles labor matters involving federal employes and their unions.

McKee, 56, formerly was director of government relations for the General Mills Restaurant Group and chief of staff for the New York State Assembly's minority leader in 1978. From news services and staff reports