You may be able to pick up a sheet of the thin aluminum they use for printing things like business cards, etc. A former employer had a small in house print shop that made stationery, business cards, etc. They threw the old sheets away, picked up a few for free - lifetime supply of thin aluminum sheet. Very useful for scale rear window straps, bumper fairings, heat shields (see my Olds 88 LMS) interior tin, anything. Can also be embossed with rivet detail using the end of a ballpoint pen.

While I didn't do it a lot, a good sharp new hole punch will knock those discs out of plastic or the aluminum like nobody's business.

To get the slightly conical shape of some headlight covers from the olden daze when they were in fact, round, check the drill bits on your workbench. Sometime, the shank end will be machined to a gentle cone. A good rap with the mallet will make a button-type indentation that can be cut with a hole punch or a sharpened piece of tubing.

Failing the end of a drill bit, a hardwood dowel can be chucked into a hand drill and shaped with a file and sandpaper to the same purpose.