Help Plz!

[socrepuscular.livejournal.com]

Sorry for bugging you guys when I'm just asking for help, but I have a query and this group is the only thing I think can help. 

I am going to be a troll doll for halloween and I need a giant plastic gem. I'm thinking like 4-6 inches from top to bottom would do it. I can't think of place online or irl that I could find this and google has produced no leads. I would be forever greatful if someone had any ideas!