Good idea to classify trim pieces by polished stainless steel, bright anodized aluminum, chrome plated steel, chrome plated pot metal, etc. A different vendor might be needed for each type.

There are dozens of vendors listed under Aluminum, Anodizing, Chrome, and Stainless in each 400-page monthly issue of Hemmings Motor News with its yuge classified section filling up more than 3/4 of each month's magazine. A few samples from the Services Offered Section in the photos. Free trial subscription here: https://www.hemmings.com/subscribe/trial?ctry_cde=USA&pub=HMN&source=freetrial1

Hemmings Motor News is to automotive what the Wall Street Journal is to investing.

Another excellent monthly magazine is Hemmings Muscle Machines, with ads but without a classified section.

For '68 Barracuda tail light bezels, Layson's Restorations sells new castings for $395/pair that might be about the same price as restoring originals. They claim the metallurgy is better than original and less subject to pitting and oxidizing.