Be sure to make a visit to the "Deutsches Klingenmuseum" (Blademuseum)
www.solingen.de/klingenmuseum in Solingen. Solingen is real close to Duesseldorf and you should be there in no time.
Definitely pays off as the museum has everything from historical pieces to modern custom knives. When you're in Solingen you'd probably like to visit the Puma, Eickhorn, Böker ... factories there. They also seem to have factory sales at reduced prieces if my memory serves me correctly.
If I were you I'd just post this question on the german
www.Messerforum.net (english will be just fine). There are lots of collectors and makers there that could sure give you some more detailed advice, or invite you to their shop.
If you're interested you can come by my shop here in Stuttgart (the town of Porsche, Mercedes and Co.

). The Porsche museum and factory are located only 5 Minutes from my home, in case you should be interested in cars.
Depending on wheter and when you would come by and how much persons you are, you could even spend a night in our guest room. (A russian friend of my brother is staying a night at our place sometimes in the same week, so that has to be considered

)
Let me know if your interested.
Regards Marcus