I had to fix one of the front fog lights as the glass was broken. Both lights had become very gray and old-looking so I decided to replace the glass in both of them. I discovered that the fog lights were from an old Porsche 993 and not the original Audi S2. The front fender is an aftermarket fender which does not use the original lights.After a bit of searching, I got hold of a set of replacement glasses on eBay.
The glass replacement was a straight forward job. A little fiddling getting the old glasses out, but it turned out ok.