Previous posts on this subject identify Hauser & Miller or
Enamelworks in seattle, alloy is 80% fine silver, 16% copper, 4% zinc
if you wish to alloy it yourself.
While other "orchidists" may have had different experiences or can
suggest other techniques, my experience with fixing a bezel or tube
setting in the enamel in the absence of soldering is the subsequent
enamel cracking or complete separation of the finding from the piece
when actually setting the stone.