Thanks for the feedback guys.
I should have mentioned in my OP that it is a metal CP with a plexi overlay. That being said I think buttons with a screw underneath would work best.
Those Yenox buttons look like they would do the trick.
divemaster - do you have more info on the shorter Happ buttons? I found some on Happ's site but they were not short enough. I need to place an order from you soon anyway.