Thanks for the link, Titchgamer - even if I am cooling on the idea, it's good to know where to go to find these. Thinking about this going from "on paper" to the real world, it definitely seems like it won't be as good an idea for the look I want, especially given the ambient lighting in the room. Also, at $10 pre button, that's not the place I want to put the money.
I think the final straw is that all the LED buttons that are translucent seem to also be flat, and I really wanted to stick with concave buttons since it's what I grew up with.
fuchi_jeg: that's a really helpful way to put it. I'm definitely looking for streamlined. It does not need to be old-school authentic, but I don't want it to be "busy" and modern. The LED buttons would have just been one color per player, no attract mode, no flashing patterns, etc. Now that I've thought about it, I think I can get the same look/feel with an all-black cab and some simple accents on the CP art (rings around the P1 and P2 button sets, a nice gradient, etc.) If I pick a simple "electric" pallette in green or blue, I think I get the feel I wanted without the hefty investment in the LED lights.
Thanks to everyone for their input!