This forum has been very helpful. I also called Grohe and the helpful service rep told me that my 7-year old facet was still under warranty. They are sending me two complete stop valves free of charge. However, I also found the o-ring set for the valve stem & stop valve exterior (47 045) available online at Guillens. Although this is listed for the 34 434 facet, don't be deterred. The stop valve 08 355 is the same as for the 34 436 facet.