Hey folks, thanks for replies. Actually I now have contact with Audio Technica US (my japanese are very bad) - and a very nice person writes to me about the opportunities. It seems, that they will do a repair for 25$ + shipping. And I will ask if it's ok to just send the headband.
@nc8000: yes, it's the headphones, that I bought from you. It was just a little accident, think maybe a child was a little bit involved. The phones are so great and no, I'd not settle for a replacement, as I guess that would be a different phone...
I'll follow this one up, so others can benefit from it later on. How do you post a pdf in a thread? James from Audio Technica US has sent me a list over the parts names, with pictures and everything.