I'd worry about clays. The only ones i know of that can be shaped accurately enough to make a decent looking part are temperature sensitive and/or non-hardening. I'd definitely take an opportunity to try out some plastics and FRP materials. They'll last many times longer, look more professional and there are lots of people here who would be more than happy to share their experience with you. If you want a starting place, I'd say look at some different kinds of foam. I know the stuff they arrange flowers with at the floral shop is a cheap and easy to shape type. Also check out some of the hand-workable Renshape foams at www.freemansupply.com. If you can make the shape of the bezel in foam, you're halfway there. Here's a few things i carved out of foam and just applied some simple finishing techniques to. I can email you a more detailed write-up if you like. Good luck!