Narwal ..... where are you and what parts do you want? .... It is your right to fix your own car and if they won't sell the spares over the counter then I would tell them you will be writing to GM Head Office ..... you need to find the address via the Internet. First time I've heard of this problem. Sounds like a dodgy dealer!
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.