Silver rings oxidation rubbing off

I have a client that wants simple silver bands, oxidized. I am having
trouble with the finish rubbing off after time. Is there any solution
to this? I have tried sealer and wax, but these don’t do the trick.
Anyone have a suggestion? Or any other ideas for black bands. They
don’t have to be silver, just 2mm black bands to stack in between
some palladium bands. Thanks