Radio shack has solid copper, 24 ga, speaker wire. 3 or 4.99 for a 75 yard spool + 150yards of wire.
I stuck out at my local craft stores and wally world for copper wire.
I think I read in another post that a guy takes the copper wire off of dead electric motors. It should be small enough, comes off in good tying sized pieces and is free.
Check you local landfill swap meet, recycling center, thrift store for dead motors.