Sorry, I can't remember where I've found him; but he was present as a white dot on the minimap. (I think it was one of the upper left sectors..)
You have accepted the quest "Let's start the adventure" (the one which needs compass/lamp/..)?
Otherwise, Mr. Brown won't show up. (If he still does not, try to reload the game after accepting Mugridge's quest; I don't know if the problem, that a new quest giver doesn't appear on the map immediately, is fixed yet)