Advice for UG watchmaker in Switzerland north Italy or near Dusseldorf please.

A friend has a UG Tri Compax Calendar Moonphase with, I guess, a Cal. 481. He lives in southern Switzerland but visits Dusseldoef so either could be good for him.
His watch badly needs a service and if anyone can advise on a trustworthy watchmaker in either area it would be much appreciated.
thanks in advance.