If you are not in a hurry, I have noticed loads of these available at the World of Commodore show in Toronto that I have been attending again the last couple years. The show is in early December and I am planning on attending once again. I have started a file of items that I see members looking for so I will add a set of AmigaDOS 3.1 books to my list. No promises but I will definitely have a good look.
Regards,
Peter