check out eBay; type in 'Audi Black Gloss Decals' mine were from a company called underground parts.
mirror casings are going to be more difficult, Plasti-dip spray might be the way to go. I've ordered a can of the Internet and the cool thing is once you've sprayed the wing mirror you can peel it off if you're not happy.
might try Plasti-dip spraying the Audi ring Decals on the car without taking anything of, as you spray the general area and peel off what you don't want, safer than ripping off existing decals. Will post up results in a couple of weeks.....