I have ordered heavy gauge silver wire, and just about ANYTHING in
precious & semi-precious metals as well, from Hoover & Strong.
Here is their link: http://hooverandstrong.com/
They will also make for you heavy/thick walled sterling or gold
(seamless) tubing, even if it something they don’t regularly carry.
There is a small charge for custom orders, but they are nice people,
and can do just about anything. Toll free Phone #: 800-759-9997