The randomly spawning vendor is probably one of the more frustrating aspects of the game imo. I just plug the map seed for my world into the online map generator so I can find him, because it's total random chance to find him otherwise.

Imo, you should be able to build a hitching post or something at your main settlement that will summon the trader instead. Plus it makes more sense for a merchant to actually be near his customers vs. some random spot in the woods somewhere.