Discus CS wing water dump seats (seals)

Per Schempp-Hirth, I am the owner of a Discus CS with NON-Schempp-Hirth water dump seats on the wing dump valves. Per S-H, ALL S-H, including CS's, have aluminum discs for seats. My ship has what appears to be rubber or similar material for seats. Soon, they will be leaking and though I think I have figured out how to replace them, I am open to suggestions from anyone with first-hand knowledge of replacing non-aluminum seats. Big question for that person(s) is where do you get the part? And, what is the serial number of your ship?

Related question: if you own a Discus CS, would you please look at your seats (underside of each wing, near root) and, if you find that yours are NOT aluminum, let me know the serial number so that I can bring S-H that information.

Visible on my seat is a rubber seat in the center of which is a brass hex head with a female 8 mm thread for the pull-down tool. Standard S-H is simply an aluminum disc with and 8 mm female thread.

I am listed on the SSA website and you are welcome to contact me directly there if you prefer.

Thanks for any help.