Hi,
I had to replace the whole wing mirror on my 6 just the other day. The covers are easily removed and can be replaced. I got a whole unit and cover for £60 online. Covers are next to nothing. Some sites also offer the option to color match with your car (if you have color matching wing mirrors).
Just be careful removing the cover. Use a small blunt knife to ease off the cover. It will come straight out, but watch for the clips at the bottom that hold it on.