Woa! Are you sure they're not available? Per the federal government, car manufactureres are required to maintain parts inventory for many years beyond the life of a car. I don't know the time off hand, but it is way more than 6 years. Surely the feds didn't let GM off the hook due to the bankruptcy.
Parts.com lets me add a fender and begin the checkout process, which supposedly confirms availability of the part. Maybe you were told wrong? I would check around with more dealers, local or online.