Newbie request for advice

I was asked by a friend to try to produce a ring for a costume she's
working on from an animation series called Utena - it's a sort of
silver and pink seal ring.

I managed to turn out a version I'm quite pleased with by cutting the
top off a domed silver ring and filling the hole with pink Fimo, which
I then baked in. You can see my effort here:
http://www.thenoodlebowl.com/jongleur/ring.html
I drew the design on by hand with a CD marker pen, for lack of any
better ideas.

However, I've now been asked to turn out a whole lot more of identical
pieces, and I'm thinking that there must be a better way than cutting
up rings. If I can find some blank silver-coloured signet rings of the
correct shape, can anyone advise me of the best way to create the pink
and black seal design on them? I assume a thin sheet of Fimo would
break off much too easily... I'll try anything but the simpler the
technique the better, as I'm totally new to this.

Thanks kindly,
Tasha