Which Nash book? Nash wrote seven available is several different printings; George Bird Evans put together two; and Nash's autobiography was mostly written by himself, but was edited and put together by Dr. Dyrk Halstead and Steve Smith.
Try abebooks, ebay and Amazon. I'd imagine any large metropolitan library might have some of them on the shelf. Years ago when I got a "stack pass" at the Library of Congess, there were all of the original Derrydale editions sitting there gathering dust. Probably hadn't been touched between the time they landed on that shelf in the 1930s and when I got my fingerprints on them.