You can search for new and old books on these bookseller sites:
David Foley-Sporting Books
76 Bonny View Rd.
West Hartford, CT O6107
The Museum accepts donations of collectible and contemporary books on fly fishing and maintains a library of every book they can find, rare and otherwise, on the subject for posterity and scholarship. They receive more than they need and resell the over-stock to raise funds for this non profit. Check out their book sale by clicking here.
A helpful site for finding vintage books as well as some bargains.