Found a place that sells heated seat elements.
http://www.sportsimportsltd.com/seatheatac.html
They also have oem GM elements (which I suppose you can buy from your local dealer). I don't know about the aftermarket elements but the heated seats in a GMC Denali (Yukon) were the best I've ever used (especially after a long day of snowboarding

).
Seems like an easy hack. Anybody wanna try and let me know how it works?