The Reagan administration might have a pleasant job open for someone who is comfortable in striped pants and has always wanted to live in, say, Benin. Or Mozambique. Or perhaps Mauritania.

Those countries are among 10 around the world that have an empty spot in the U.S. embassy where the ambassador should be. And while most of the juiciest plums in ambassadorial appointments have already been snapped up, a few nice spots are still open. The Bahamas, for instance.

Or for a little more excitement, perhaps Afghanistan. If not that, there's Ecuador, Ethiopia, Indonesia, Laos or Rwanda.

If none of those appeals, there's always the possibility that a more enticing embassy will open up. "There's never a time when all of them are filled at one time," a State Department spokesman said yesterday.

Nominees to three other ambassador-less nations are awaiting the formalities of Senate confirmation. California realtor Theodore C. Maino has been named ambassador to Botswana. William Alexander Hewitt, a California businessman with a long list of national and international credentials, is in the hopper for Jamaica. Fernando E. Rondon, a career diplomat who is already ambassador to Madagascar, has been nominated to handle ambassadorial duties as well for the Comoro Islands, a volcanic archipelago off Madagascar.

A 14th country got its ambassador just this week when James M. Rentschler, a career Foreign Service officer, was sworn in for the post in Malta. Rentschler, who has served for the last five years as a senior member of the White House National Security Council staff, will be the Reagan administration's first ambassador to the strategically located Mediterranean island nation. Joan Clark left the post in early 1981.

In other ambassadorial news, President Reagan announced yesterday that he will name career diplomat Rozanne L. Ridgway to be ambassador to East Germany. That doesn't close any vacancies, however. East Germany already has a U.S. ambassador, Herbert Stuart Okun, whom Ridgway will replace.