Call around to local hobby stores and ask if they have a K&S metal display, The copper they carry is a good aloy that seems a bit harder then say typical copper wire and takes a good shine
Also if you are cheap like me and have some copper wire laying around 12 agw or thicker you can stick one end in a vise and the other end in a drill and make your own rod, I swear its like a miracle, you can take a bent up piece of garbage and make a perfectly straight rod by pulling and twisting at the same time, and it seems to work harden too ;0)
EDIT The wire needs to be round to start with, egg shape or flat on one side will not work