there are quite a few around. we had a thread about this awhile back: http://www.bikeforums.net/folding-bikes/943005-have-you-tried-h-s-folding-handlebars.html

xtasy folding handlebar

doppelganger bicycle folding handlebar

there are others, i'm sure. there's probably a solution for you located somewhere in this pile of searches...

there's also this: looks a bit iffy....