Big Hat Logan sells a copy as well.
Initially he is found in
In order to unlock him as a merchant, and to have him appear in Firelink shrine, you need to do the following:
Big Hat Logan is found in a cage within Sen's Fortress. After getting past the second platform containing swinging blade traps, you'll quickly come across a sleeping snake guard leaning against a wall. Big Hat Logan is located in a room hidden behind this wall, only accessible by breaking the wall.
To break the wall you need to redirect the metal balls you see throughout the fortress. The mechanism to do this is located after the second room with the metal balls coming at you. you want to redirect the mechanism to the hallway opposite the exit which will simply drop the balls off the game map.
In order to unlock the cage he is located in you need one of the following:
- Master Key: This is a possible starting gift, and the Thief class will always start with it.
- Cage Key: This is located further on in the fortress, shortly before fighting the boss. On your way to the boss you'll notice that part of the bridge is broken. If you jump over this (dash + action button) you'll find yourself in a tower with a merchant, and at the bottom of the tower you'll find the cage key.