Thanks Paul,
the O-ring we meanwhile also sourced in Japan. But what we intend to is to repair some of the booster units completely for 7335 and 750 E32 and have them ready on stock for our club members. Especially on the 750 it is really difficult to get the booster unit out, and therefore we plan a complete overhaul of the booster units with all replacable wear parts, just to make sure that they work 100%.
So the best would be if we could get hold of the original ATE repair kits from a reman company which might sell it to us. By some legal/liaility reasons or company policy of ATE I cannot get them in Japan or Germany.
So if you find out a company selling us the original repair kit, that would be the best. I would buy some at one time.