Making a jeweled cat's collar is a lovely idea, and putting a silver
"bell" on it to "bell the cat" an even nicer one.
But before you go to all the effort of making a rattle, gong, or
whatever you want to call it, be sure that it will work to protect
birds and other prey. I believe that your average smart cat can learn
in less than half a day how to move silently, even with a bell on its
collar. Cat collars are sold with little "jingle" type bells, and
they don't work at all. Years ago I systematically increased the
number of noise-makers on my cat's collar, but he always quickly
figured out how to move silently in spite of their presence.
Occasionally there would be a noise when he jumped into my lap, but
it never sounded when he was outside stalking something.
This fact may have something to do with the national movement that
is trying to persuade cat owners to keep their cats confined, in
order to reduce the carnage among birds and other wildlife that
results from letting them outside. Hope this helps,