craftgrrl | Help with a costume?

Hello everyone,

I lurk here more than I actually post, but I am in a quandry.

I am going to my first really big convention, and I'm cosplaying as Princess Peach. I have everything i need, except the jewelry she wears. I've got the dress, I've got the wig, and I'm working on the gloves.

I can't figure out what to do. I can't sculpt, so clay is pretty hard for me to do, though if that's the only option I'll do it.

I would -love- to have the jewels actually be JEWELS, not styrofoam or anything like that, but I can't seem to find any big enough for the brooch thing on her chest. I'm thinking I'm going to possibly use craft foam as a base for the crown, but I'm certainly open to suggestions for that too (in fact, I'd love to find some sort or actual metal type thing to use.

I'm going for a "realistic" version of this: