So I've dealt with one of the companies I am about to talk to, and they are really great to deal with (both pieces would have been free, had they not cut them for me)
First place I'll talk about is Regal Plastic Supply
. They are local to me, and have been "the hookup" for the bits of plastic I've needed. The first piece I was attempting to use as a gasket for my scrap-aluminum pocket rocket (failed experiment there...ended up paying $7 for a damn o-ring) Anyway, they gave me like a 12"x12"xsomething sheet of some type of plastic to abuse with the understanding that if it worked I would pay them $5. Well, it didn't work so it was a freebie. Today I paid them another visit. I'm getting rid of one of the 2 last components from the junk ABS fender eliminator off of flea-bay. The guy cut me 2 (only needed one, but it's nice to have an extra in case I screw up), and only charged me $5 because he had to cut it, otherwise I probably would have went home with a 8"x24" sheet to mess with. Man I really need to get a shop. Anyway, they can do some really cool shit at their shop. They have a CNC router that they can use to cut, shape, and "engrave" plastics. Couple the engraved plastic with the Emeralight stuff they sell, and you can have a really kickass sign!
The second place may have been mentioned here, but I'm such a forum whore it could have came from a number of places. I dig the idea, and will likely use them in the future for other projects. Anyway, if you've got the time to mess with stuff, and want custom plastic/metal pieces made pay a visit to eMachineShop.com
I think it'll be an awesome source for prototyping/final production...if you are going to do things en-mass.