Also try Pololu.com I think I rememberseeing a serious servo, that will run off of 12VDC but can lift up to 200lbs. Im sure thats a bit of overkill, but they do have a selection of others. I myself, might at some point get one of those monster servos, I have an arm design that is in need of lifting at least a 150lb human with ease (for a medical design).