For GM cars......2 Din Xenarc mounting brackets $105 with shipping.
A couple of sites that will do custom piece work
Custom metal enclosures
Reasonable prices with great Customer Service. Steel only. Solid Construction. Downloadable software for part design.
They made my case for me, and I love it.
Custom panel fabrication
Reasonable pricing, Design your part and get a price quick. Downloadable software for part design.
Thought about making a Custom bezel for my Touchscreen here. I ended up using extra parts I had lying around.
Downloadable software for part design. Many options, laser, Water jet, etc...
Can be pricey for 1 piece, but you can get 10 for the same price, depending on what you are doing. Would be good for a short run. Wasn't worth the cost for a 1 piece run for me. If you are trying to duplicate 10 or more pieces, it might be worth it. Plastic, Wood, Aluminum, Steel, Copper, etc...