I did also have a pair of DerDau's made, about 25 years ago. At that time, they were considered a slight cheaper option for custom boots with less wait time than either the Vogel's or Dehner's. I still have them; I have elastic gussets put in them a few years back as I had them made when I was thin and fit. The story I vaguely remember is that the DerDau guy was an apprentice at Dehner and then went out on his own? I was perfectly happy with them but obviously customer's more recent experience in more relevant.
Journeymen in Middleburg used to make custom books, but I don't know if they still do.