Have you tried an engraving supply place, or trophy place?
If you can just find the metal, it doesn’t have to be self-adhesive.
There is a product sold in the crafts world under various names,
such as “Killer Adhesive” and others – it’s flat sheets, very
strong. The backing paper is salmon colored. Let me know if you
need it and I’ll try to find you a supplier.
Metalsmith, Certified PMC Instructor
Hard to Find Tools for Metal Clay