The cameo backs I bought online were originally silver and sold in a 12 pack, the flur delis I made a cast of and hand pressed FIMO clay into it to reproduce the shade. Once i glued them on I spray painted the whole thing gold.
Etsy is a great place to find jewelry finding including Cameo Base Setting.
This is the style I bought.
More from etsy
Also has more option if you want different backs for the manga interpretation as seller tend to have more then on style in there stores.