I think it is Bosch No. 1 427 232 003 (Druckdose). Same for R24 and R25.
Great, thank you - you are a champ!
But I see by searching on the part number that it is not something you can easily get your hands on. Don't seem to pop up anywhere.
In any case, I have not really tested the one I have, and it sort of looks ok from the measurements in the manual. But if a new one was cheap and easy to get, I would have just replaced it to be sure it works.
How much shims do you have under your barometric compensator?
When I took mine off, I found one shim of 2 mm and another one of 0.1 mm, so in total 2.1 mm.
Thanx,
Christian