I have never seen a ball and seat wheel in Europe. I looked through a catalog of KS which is kind of the equivalent of our Ken Tool. http://www.kstools.com/de/flippdf/K11/Lkw/Lkw_D/files/lkw_gesamt_ob.pdf

I can't find a square socket for the inner nut. If you can't find one in Europe, I will be in Germany middle of next month and it is reasonable to mail something within the EU. A made in USA inner nut 1" drive socket can be bought for about $36 which is about €27.