I have been online looking for information about FKKs in Hamburg. I found some sites but, they were in German.  Lots of info on Berlin and Frankfurt but, little about Hamburg.

In and arround Hamburg I am not aware of top class Clubs. But the adress to go is Atmos www.atmos-fkk.com (english)
I guess there are usualy some 15 to 20 very nice, mostly german girls there. Entry is EUR 60.00, Food and non alcoholic beverages incl. Girls charge EUR 50.00 per half an hour.
Currently they refurbish the place, and whats allredy done looks great.

Hamburg has more FKK style clubs today then years back when all they had was the Reeperbahn, a place one should just window shop and avoid. Its known for sex shows and pretty women but buyer beware. Atmos is  the big player however a bit more expensive then most. Even if the name of a club has changed google the address as it may have re-opened under a new name. This is common with FKK clubs.