Pennytech Jumper Cables
This ought to cost you all of $7 or $8:
Go to Home Depot and get 8 feet of 12 or 14 gauge (two lead) Low Voltage Lighting Cable from the spool in the Electric Wire Section. This is the stuff that's used for low voltage yard lights. It's very flexible. That's gonna cost you about $0.35/foot. Don't get the pre-packaged stuff, get it off the spool.
Next stop is at Wal-Mart to pick up two sets of small battery charger clamps from the Tire Section --where they sell battery terminals. That'll cost you another $1.88 per set.
Take everything home, split the wires back about 6 inches on both ends & solder the terminals to the appropriate ends of the wire, being sure to observe polarity.
If you've got any heat shrink tubing on hand you can slip some over the ends of the wires before attaching the terminals. That will stop the wires from separating further.
Remember, it's a jumper cable, not a starting cable. It's not gonna work if you try to start a car with it.