Leon can be found in Yanille's hunter store. He sells the Hunter's crossbow for 1300 coins. He can also make the kebbit bolts used by the crossbow and sell them to you for the components of the bolts and a small fee.
Trivia
Ironically, Leon, if used as a name, means "lion" in Latin. The fact that "he seems to be making odd sucking noises with his teeth" implies that his name has a purpose.