.
I like to think outside the box...…...
When I want an off-beat medallion, I cruise the jewelry counters of a few second-hand shops, looking for a perfectly round fashion accessory (cufflinks, tie tacks, earrings, etc) in the diameter I want/need.
Using a silver coin is another option - I used a US Indian Head Penny on a rifle in .250 Savage, that looks like it grew there.
I have also converted a woman's broach from one store into a grip cap for a knife I re-handled