Is it cosmetic rust or are the rims actually pitted and damaged? If it's cosmetic rust then you can use tin foil dipped into salty water to rub away the rust off of the chrome. Yes it sounds mad, but it works!
If you needed to replace the rims though, I'm not sure where you would buy some brand new, I don't even know if any one produces them anymore.
Personally I would try either
ebay Kleinanzeigen, or have a trawl around the local bike shops for some old wheels. I don't know where you are in Germany, but where I live, we have several old school bike shops that are a treasure trove of old parts. I managed to find some obscure spares for my wife's Sachs Torpedo rear hub in one shop.