I spliced in about 6" of spare brown 16/18 gauge copper wire that I had laying around in the garage. I used (2) 16-22AWG butt splice connectors to splice the wire in line and connect it on both ends and crimped them on with pliers. I then wrapped the connections with black electrical tape and then re-wrapped the wire bundle/harness so it looked semi-professional.
Here is a thing I mocked up to give you a better idea of the in-line splice: http://imgur.com/5fUrbjJ
If you don't already have this stuff laying around your house; butt connectors, electrical tape, and 12" of wire should run you about $5-10 at Lowes or Home Depot.