The only place's I have found have been:
Audi - £770
Hoffman cats - circa £450 for an A8 4.2
Some eBay company do a pattern one for circa £350 but it looks pretty poor.
A8 parts don't have any, eurocarparts and gsf don't do them, and all German don't do cats.
Are the 3 places above really the only places to get cats?
this isn't looking good. Do A8 4.2 cats of the same era fit an S8?