I just picked up some RGB led wire off ebay for cheap.. .99 for 3meters.
can always strip them apart for separate wire... pretty sure it's 24awg, might be 22.. check ebay there are a lot of sellers on there.. it's 4 wires Red, Green, Blue, Black.
The buttons carry next to no current @ low voltages, it's really just a matter of what you can get cheap that's not so thin to give you problems.