yeah i had seen that thread when i initially searched for info on them but the GM dealers i have talked to knew nothing about them or how to get parts. I assumed they outsourced them from another manufacturer because they look alot like Race Runners:
http://www.racereadyproducts.com/racerunner-shocks/racerunner-20-bump-stop/

I was going to try and call sway away who owns race runner and see if they can get me a seal kit.