O ring/seal for safety valve of Karcher SC2, SC4 etc steam cleaners positioned as per second picture.  Equivalent part no. 6.363-468.0 and made from the correct EPDM rubber for this application.  As a check, inside diameter is 22mm.

Listing is for two o rings so you have a spare for little more than purchasing one.

Listing is for o ring only, valve only pictured to confirm positioning.