The process most of those companies you listed will use is vacuumized aluminum which will then be covered in a clear coat, while nice in appearance, it's very delicate in nature, IIRC on the 73-4 B Body hand crank sunroof handle well it has a copper base under the nickel/chromium plating, the only place that I know of that can copper/nickel/chromium plate a plastic part the way the factory had done is Advance Plating in Nashville Tenn.

Family run business, top notch work, but expect to pay for that work, Steve can/will do mail ordered quotes/work/shipping on your parts

mike