C5 A6 inserts are the same as the D2
I just knocked a set out of each type of upright and they are identical.
As for part numbers, thats a bit harder as the units I have here don't have a recognisable number, but I think you need 4B3 407 253 G and 254 G. Its hard to tell as there are dozens of variants, but C5 facelift 2001-2005 with alloy uprights and bolt-in bearings all use the same control arms so should all have the same inserts.
Prestige don't appear to have any and I can only find three on ebay which may be the right part. Obviously I have a pair here as spares for my A6, which after careful consideration I am willing to sacrifice for a D2
I'll pm you so we can work something out.