Most if not all electric shields work on AC power. (disclaimer, don't hold me responsible if I'm wrong!) Just hook it to any AC in your sled. I just hooked mine up last night, had an extra plug on my MXZ that had power right by the oil tank. No battery in mine either. I tested it with a multimeter on AC when the sled was running. Works great! you'll probably never go back to a non heated.
You should tie into the hand warmers under the handlebar pad. Make sure you use a test light to find +/- and if your not going to sauder I would probably cut the wires strip them off, get some shrink tubeing and twist your wires together as tight as possible and them shrink tube them but if you can sauder it I would recommend it.