I have made hundreds of pinhole for workshops i used to lead. Pop cans works, i like brass shims like Donald said. The trick is to us a ball point pen and tap it on the shim or can, you get a divot on the back side, flip it and use sand paper to sand said divot. Now you have a lot less material to go through.
Using a sewing needle that you flat sand on one side ( think drill bit now) i glue them onto clothes pin with epoxy, cut the top of needle a bit shorter with snips, put you finger on top of the needle and flick the cloth pin (manual drill)...
A size #10 sewing needle will give you 0.46mm- size 12 0.= 36 ( its an art form not a science) .
Make multiple version that can be identified, try them all see what you like. Sometime less than perfect pinhole give you the best results.
Have fun