Well if heat it is, are you resourceful??
I went out to my Saab graveyard and pulled out a grid from the heated seats. I made my heated vest out of the same thing 12 years ago. All you need to do is find a back support and either slip this inside if it is 2 layer, or go buy some sweat shirt, or fleece type fabric from the fabric store and sew away.
This piece is made to run in series with the bottom grid, and is electronically controlled in the car, so it needs to be regulated! By itself it draws 15 amps and heats up very fast and very hot. Me being the farmer at heart, would probably try to find an old dash light rheostat to make a controller, and mount it somewhere under the seat with a dedicated cord to the pad. I am sure radio shack might have similar, or there are controllers that Gerbings etc make for there heated clothing that should work.
If you want to give it a shot send me your address, and I will drop it in the mail.
