Just in this second, I've sent a mail, to Andreas Bauditz, the secretary of that club:
http://www.audi-100-coupe-s.de/ and writer of that book:

http://www.amazon.de/Audi-100-Entwicklung-Technik-Design/dp/3898808998/ref=sr_1_40?ie=UTF8&s=books&qid=1212333460&sr=8-40

if perhaps he knows more.

While searching, I've seen, that annother guy has written annother book like this about the Audi 80. Do you know it?



By the way: next weekend I want ot go the the oldtimermarkt in Bockhorn, the biggest spare-part-market in Northern Germany. Shall I look for some special literature?
You should visit markets in Southern Germany, at best in Bavaria. Closer to the the Audi-factories, you'll have better chances, that employees from there are selling internal stuff.
So several of my "specialities" of my K 70-literature-collection I got from VW-employees.