Bender - go check out
http://www.lizardlick.comThey have a great selection of Sanwa and Seimitsu parts, and ship super fast. I've ordered a ton of parts from them.
The sanwa buttons aren't going to be as thin as that button you linked because they have external microswitches (that are a lot nicer than the ones on that button) I can't find a tape/ruler anywhere handy, but the sanwa screw-in i have in front of me is probably just a touch over 1" tall, going from top to bottom of the terminals.
If i'm understanding your clearance issue correctly, I think you could make the sanwas work if you got screw ins. Route out a hole a little larger than the button and mount it inside the hole