I use aluminum plates from printing presses. They can be cut with scissors or a paper cutting shear, and pencil seems to be permanentn on them. Of course thy can be scratched too, but I stopped scratching them since the pencil works so well. But it’s not just aluminum, there is some kind of coating on them. You can usually get them for scrap prices and cut them to any size. I use copper or brass wire. Only caveat is to poke a small hole and twist the wire tight around the tag so it can’t flop on the wire in the wind and wear through the hole. I can’t imagine any gardener or fruit collector regretting getting a stack of them. They make good vole guards too.