Are the toes of the socks shown in your shop closed by hand or are they sewn with the machine?
I know that the hand closing is finally made with the special machine also but
the pics show 2 lips which is the typical sign for the sewing.
How about Breuninger? Or Braun? You could also try Ansons and P&C.
Ladage & Oelke in Hamburg. Or Hirmer Herrenmode. Eckerle.
You might want to call a Frankfurt based accessoires store named Molani and ask for Mr. Oertel (the owner). As far as I know, he sells socks from Bresciani. Good luck!