Okay, I just met you...and this is crazy but why don't you just take apart a regular push button, drill a hole in the middle and mount a smaller switch in that hole. Just make sure that the center mini switch has a lower activation force than than the outer and you'll be fine.

+

= #winning.
If you used all black buttons it would be pretty seamless
I mean, honestly, we're a community that builds entire arcade machines, stuffs lights that blink how we want them to inside of buttons, and can autorotate CRTs and the best mechanical hack we can come up with is using some off the shelf butt ugly blue and red abortion of a button? Jeesh crackers. Think outside the box people. What about putting using a metal outer and a plastic inner and having the metal outer be touch sensitive? I bet you could hack a button to where a half press will give you one input (coin) but a long press will give you another (start). Should be doable mechanically with some hot glue and a stick or electronically with some relays.
Or you could just drill a wee small baby hole and mount a mini button.