There are several companies that make battery heated clothes, but their products can cost over $200. You can make your own batter heated pants, jackets, shirts, gloves and socks for around $50. Most of the supplies you need can be found at a RadioShack, Walmart, or Home Depot.
Plan your layout for the wiring. You'll want it to be in the front where the wind hits and where you won't sit on it. If you're making pants, the wire should start at the crotch of the pants and continue down the inseam, then continue back up the legs with a wave pattern on the shins and thigh. This will make it easier to put the pants on and sit down.
Turn the material inside out. Measure out 30 ft of Teflon wire and mark the halfway point. Thread the wire through the clothes in the pattern you laid out.
Solder the Teflon wire to the thicker copper wire. Then bend the Teflon wire down, leaving some slack, and tape it to the copper wire as strain relief.
Add a connector to the end. Tie a knot in the copper wire and thread it through the pants; this will act as a strain relief. Solder and crimp whatever connector you bought. Always make sure to put the female side on the power source.
Sew in a liner. This will protect the wires and keep you from getting burned.
Connect the female connector to the switch and the fuse housing, and put a ring connector on each end.
Take two lengths of the copper wire and attach a ring terminal to one end of each wire. Then, connect the other end of the first wire to the fuse housing and the other end of the second wire to one of the terminals on the switch.
Attach another wire to the other terminal on the switch and connect that to one side of your female connector.
Attach a final wire to the other end of your fuse housing and connect that to the other side of your female connector. This can now be connected to any portable battery source.