I had a leak in mine.  I surfaced the piston to be flat on top, and the old crush washer was not a viable solution, so I ordered a new crush washer.  Because of the freight, this is a PIA to get.  I took measurements so that you can find what you need with something that does not come from Porsche.

 

This was installed with Hylomar for extra sealing.  No leak at all now.

 

 

1.145" = 29MM OD:

 

 

0.877" = 22.3mm ID (it fits loose, round to 22mm):