Same issue here. I'm on my 1st play through so I really don't want to leave him behind (not sure what all I'll miss later in the game).
He's located in the graveyard and says the following :
"Let me think. A sprinkling of skulldust. A vial of dog's drool. Dried illweed. A few more odds and ends and I can get back to the ship."
The only option is to "end" the conversation.
