You can get nickel jump rings (as well as jump rings in nearly any
metal, including the recently discussed Iconel) from
http://www.theringlord.com. They mostly sell them in inch sizes, but
I'm sure they'd be happy to do a custom batch for you. The ones in
stock are sold by the pound and are not expensive.
Check out the newly added gallery to see amazing chainmail stuff,
including (of all things) a chainmail backgammon board and the
coolest candle holder ever.
Usual disclaimers apply - I'm just very fond of metal rings being