Triathlon shorts are very comfortable - small thin pad, just enough to keep you from getting irritated by the shorts themselves.

It might not be enough pad for you, though, if you like thick architectural padding and just want to find a smaller one.

TE sells a good selection of tri shorts. (I get mine here) http://www.teamestrogen.com/categories.asp?catID=65

I have the same problem you have, but for opposite reasons; in that my sit bones are so wide that they don't even land on the new architectural chamois, and the whole thing ends up between my sit bones (instead of under them) and works into a wad that crushes my soft tissues. Tri shorts solved the problem for me.

Edit to add: and tri shorts generally run kinda small so you shouldn't have a problem finding a pair small enough.