Not sure. If it were me, id just make it out of some good 10 gauge wire and a 40A relay or something. if you go that route, make sure you add a fuse or fusible link in on the power wire into the relay.
Ozz: running that kind of wiring isn't a good project for a first timer or someone who doesn't know a lot about electrical circuits. Im not saying that you dont, because I don't know your background, but be sure you know EXACTLY what you're doing before you start, or you'll wind up with a LOT of problems. if you arent sure, spend the money for an aftermarket harness.