A local junkyard would probably be your best bet because you wouldn't have to pay shipping so more than likely it would be your cheapest option.
As far as eBay goes, I found a company that has 10 of them available. However they are $48.85 ($31.95 plus $16.90 for shipping) a piece which seems awfully steep to me, especially for one housing.
I will look up the part number for you tomorrow morning so you can look them up on GM Parts Direct. They should be pretty cheap on there.
Okay, I just looked up the part number on GM Parts Direct and there were no matches for it. I would definitely suggest just trying to find some in a junkyard then because I still think the price of them on eBay is ridiculous. Just my .02 though. I'm sorry I couldn't be of more help. Good luck.
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