I have two of these fine pistols, both mint in boxes, but sadly, without the barrel weights. I bought the first one back in 2000 from the widow of a GI who bought it new in Germany in the late early 60s, and then forgot about it. It has brown grips. The second one has black grips and is two years newer. I wrote to Walther asking about spare parts - seals and so on, and was told to shoot it and enjoy it, but not to bother about spares, as there were positively none.
However, John Knibbs here in UK might have a few bits and Laurie Amatruda repaired my LP3 a couple of years back, so there IS some hope. John Knibbs Airguns spares is in Birmingham and has a web-site. Laurie lives just outside London and is a retired engineer, but I can give you his address if you want to try him.
Best
tac