For D2: (have no idea about D3 -- just use ETKA)
4D0 919 145 -- for D2 chassis number up to 4D-X-015 000
4D0 919 145 A -- for D2 chassis number after F 4D-Y-000 001 <-- I've got this one
There are receivers for other Audi models, but I think the only difference is the length of cable supplied and shape of plastic box. I believe they all work the same way. For instance, we have 8N0 919 145 receiver from Audi TT and it looks like this:
Bracket and bolts for D2 if you need them:
1 x 4D1 919 159 bracket
1 x N 013 96 49 screw to fix bracket to chassis
2 x N 013 95 32 screws to fix receiver to bracket or to recess behind the instrument cluster
>> Are these common enough bits to find on German ebay, if it was more or less standard fit across the '8 range on the Continent?
I think all A8s supplied to countries in CET time zone (see the map in my first post) had this receiver installed as standard.
P.S. If you want to search German ebay just type "Audi Funkuhrmodul" or "Audi Funkuhr".
You need the version with wire coming out of it which ends with 4 pin electric connector.