A company by the name of GTS makes the covers. Any local auto parts type place should be able to get them for you.
They come with back to back tape brackets or ones that you can permanently screw into your car. I would never screw something like that onto my car so I went with the taped ones.
I had the clear ones on an 88 Iroc. I was pushing 500HP with nitrous and they would blow off the car under acceleration or high speed all the time.