If you are economy minded you can cut up ice cream containers or even old venetian blind slats will do.

Seriously, you can buy bundles of them from many orchid suppliers.

AND why are you only worried orchid species, what about orchid hybrids?

In the long run you are better off using #2 pencil. All ink fades or washes away. In our group we have a grower that makes metal tags. I like the white plastic ones that come to a point with a hole to tie them on. The point is good when I want to drive them into a pot.

Old slats from white blinds like Arthur said work great. And shavedmokey is right. Pencil works best. My carnivorous plant supplier told me has used a pencil for years because it doesnt bleed or fade. That's what I've done for years with all my plants.