I've posted this on the forums and thought I'd post here as well;
Awhile ago I bought some stainless steel balls, meant for jewelery purposes, predrilled and tapped. I thought of using them for a ball and socket armature, but haven't had a chance to try them out yet, and won't for awhile. They were wholesale, so I've got a ton of them kicking around - so, if anyone would like some to try out, just let me know and I'll mail them out. No worries about postage or anything like that - more people experimenting with different mediums is always good!
They're 6mm and 4mm, predrilled, though I've no idea what hole or tap size. If you'd like some just send me an email with your address and I'll ship them off!