I go once or twice a week here.
Much easier to find Zinc platers because of what Joe mentioned about environmental issues.
ATE used zinc from the start on calipers but most of the yellow hardware on P-cars is cad. And you're correct, the finish is just about the same these days in fact, most zinc shops can emulate cad so you can't tell.
The main concern with some of the parts you mentioned (latches) is the "pot metal" makeup of the guide. Take that out and have it glass bead or soda blasted if you're striving for a clean, new look. That piece will not survive the acid bath.
You have to have TONS of metal finishers in your area. And TONS of platers that are into car stuff. That's what you want to find.
https://www.google.com/search?gcx=w&sou...024&bih=677