Now I see....

....well I should have looked at my own link I guess! Now I understand what you mean.

For what it's worth, on the newer 6G and 6M guns, the same two parts are nos. 34 (metal washer with hole in center), and 35 (solid resilient washer, now with no hole in it). I suspect these will work in the older guns as well.

Part 34 is the "Justierscheibe" and this functions as a spacer. Maintaining the correct spacing as seen in the link above is critical, and accordingly this part is available in 0.2mm increments ranging from 0.2 to 1.4 mm in thickness! With new seals, your gun may well require a different spacer than it had before. I guess the function of part 35 "Vulkollanscheibe" is just to take up space between part 34 and the end of the receiver. BTW neither Babelfish nor my old German-English dictionary was of much help in translating these terms....

We are now in way over my head, in terms of ability and experience! But perhaps you could make a new part 35 out of plastic or brass, etc., shim material, and vary its thickness to get to the correct end result.