Are you speaking of the rubber well-nuts that go into the bottom of the wing and the stand bolts to? If so, they are GM part number 14005097. They are M5 - 8 with a range of .035 - .232 inch. They are available from Auto Vehicle Company (Au-Ve-Co) under part number 16248. Au-Ve-Co is located in Cold Springs, Kentucky 41076. You can probably check their web site for a local source. A GM dealer may have them since they're a standard GM item, used in most deck lid luggage rack applications.
I don't know what stores you have up there, but locally, Ace Hardware, WWGrainger, Fastenal and I think Harbor Freight carry them. I('ve also found them in some of the larger paint and body supply stores.
The metal nutserts can wear through the thin lower surface of the wing over time. Vibration or overtightening can do it. The rubber well nuts have a cushioning effect against the spoiler and they are the same as used by GM.
Check out clipsandfasteners.com They carry a good line of GM fasteners as well as for other vehicles.