If you're really determined to have a shallow brass plug, make your own. Start out with a piece of flat brass stock about 3/32" thick, cut out a round disc slightly larger than the hole you want to fill, and use something like a 2" trailer hitch ball and a big socket to put some dish in it. Then file it to be a snug fit into the counterbore and tap it firmly into place.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!