Go to Radio Shack, and look for 26 AWG Stranded wire. The more strands, the better. Better yet, go to Mouser.com and order three rolls(one each of black, red, and yellow. You can use it to make your own servo extensions. Get the 100 foot rolls and you'll have enough to last for a long time. The typical length of reciever wire is about 40 inches (1/4 wavelength at 72 mhz), but you should check with the manufacturers web-site for the specific length.

While you're at it, get one of the small "cold-heat" soldering tools (they seem to be everywhere these days). They work GREAT for soldering wires together. Keep it in the flight box for quick field repairs.

Brad