I used to have plates like that made by Grandview Aluminum.
http://www.gapalum.com/Custom_Bumper/custom_bumper.html
We sold about 10 a week at the parts store I used to work for, and I had special ones made up that I sold at swap meets. The best sellers were Oldsmobile, Buick and one I had them make up that combined the Mopar Pentastar and the Direct Connection logo. When I was selling them, the flat aluminum plates weren't as common as they are today. Sometime in the late 70's that came to an end after someone won a federal suit (I think it was Notre Dame) that kept companys from producing and selling unlicensed products using copyrighted logos.
Anyway, here's my personal favorite that I used to sell a lot of.....
Oh, they can make them in aluminum or something that looks like bronze.