Convertible Vehicles - Help finging missing part

I have a 2000 Pontiac Trans Am Convertible that I just purchased. I am trying to identify the triangular piece of metal that fits between the rear of the side window and the top.

Does anybody know what this part is and/or where I might find one?

I saw a pair on ebay for like 34 bucks that had been powder coated.

Thanks for your help. Do you know what they are called?