You can buy 'S' Line badges on Ebay complete with a little bracket for the grille. The bracket is not an EXACT match for the profile of later grilles but can be modified and with Superglue easy to install. For the pedants such aftermarket badges are more chrome than matt finish of the OE as fitted to front wings, but who cares they match the chrome rings of the grille. I know 'cos I have done so on my '09.
If you can pull the OE exhaust trims off you should be able to buy large bore aftermarket replacements as opposed to getting ripped off by greedy Audi. Those pictured don't look that bad and surely could be cleaned up.