Look in Ebay under Books: Used and Out of Print. Type in John Norman or Gor as your search.

Expect to pay anywhere from $5 US to $50 or more US for each book, depending on the rarity, printing edition and condition of each book.

There are 25 books in all. The first five don't really have much to do with slaves and such.

Please, for the love of all that's holy, don't read them like they're supposed to be BDSM bibles.