Dan, You might want to try Imperial Smelting. They are located in
Markham, Ontario, Canada, however they do have a Rhode Island Office.
You can make custom orders with them, and I have ordered fine silver
wire from them, though not square. Their Rhode Island phone number is
401-295-5060, FAX 401-295-0651. They have a toll free number -
877-994-7726.
Good Luck,
Catrina Warner