COB LED strips-- very bright, continuous strip of warm light. Easy to hook up to DC voltage. Here's an example: http://dx.com/p/diy-2-88w-3500k-270lm-warm-white-light-cob-led-strip-yellow-dc12-14v-217505 but they have them in all kinds of sizes, voltages, wattages, etc. You would likely need to dial back the power as they would be too bright and hot at full power.

Have you thought about putting the 3D models up on a site like Shapeways? You can set the profit you wish to make per unit, and customers can pick any material they'd like (nylon, brass, stainless, gold). They handle printing, fulfillment & payment, so once your model is uploaded and public, it's pretty low maintenance. You can also set if people are allowed to download / modify the model or not. The models would be unpainted (although some sites do offer 'full color' 3d prints, generally that material is pretty brittle) and customers would install their own lights, but you would avoid all the order fulfillment & mfg hassle issues.

I made a couple 3D printed pinball parts for my own use, and threw the models up on Shapeways in case anyone finds them useful (System 11 credit / start button, etc).