I may be telling you things you have already tried but a couple of suggestions: EPER is a good starting point. Also, have you tried googling the numbers. It should come up with a number of sellers (mostly abroad) of 2nd hand and or recon boxes. Some have a list of equivalent numbers, whether they are accurate or not is the question. This is where you have to form a judgement looking at as many sources as you can find. The German parts seller A. Augustin (can't remember full name) is a very good source of equivalent part numbers. If it's any use, mine is 20KM57 (from memory) and is from the 2.8tdi.