I am in the same position myself. Cannot find any one to re seal my LPM-1
Protek Supplies in Bognor have valve, breech and probe seals available, if these items will cure the problem and you have the skills to dismantle the pistol yourself. Probe and breech would probably be straight forward, but don't know how difficult it would be to fit a new valve seal, as I don't have any strip down instructions.
I contacted Chris Lacey of Lacey's Shooting supplies a while ago who told me that Walther had stopped making any parts for the LPM-1.
While the afore mentioned seals are available, I have not been able to locate a piston seal anywhere.
If you could get the parts necessary, probably someone like Wonky Donkey ( Dave Price ) would be worth contacting to see if he is taking on any work at present. DM80 could be worth contacting as well.
Good luck anyway, if I happen across a solution, I shall let you know