We've had a lot of threads about this... so many that I wasn't sure which one to update... so here's yet another one.
I have bought 5+ types of rubber feet over the past few months (mainly for HHKB Pro 2) but none have been satisfying. They were either too thick, too ugly (round = yuck), not sticky enough, etc.
I finally found some that I like. They are 2.5mm thick -- just barely thicker than the two rubber feet on the HHKB. Very sticky adhesive and very good anti-slip properties. Plus, nice and cheap.
http://www.westfloridacomponents.com/HW304APF10/Clear+Square+Small+Self-Adhesive+Rubber+Bumpons+Feet+10.2mm+x+2.5mm.html
Show Image
(http://i.imgur.com/ytMd9Nn.jpg)
Thank youu!
@kaotikb, mine was only like $4 shipping