I believe I've seen some that use 1/8" mini plugs. If that's your situation, you can buy a cheap earplug (not earphone) mono extention cord from RatShack.
If RatShack doesn't sell 'em any more (I can't find 'em on their web site) or you can't find on on a local rack, then this should help.
http://www.ramelectronics.net/html/mini-plug_cables.html Stereo will work just as well.