I was looking for a cheat to find the Vendor without too much negative impact on the immersion experience. This is what I found using console commands (I'm on a PC)

First to use console commands you insert the launch option -console in you valheim steam setting.

The in game you do F5 and "devcommands"
(Best to place yourself at the world origin point - where you were first dropped off at the boss stones)
The do "find Vendor_BlackForest"
That will give you his locations. (Once you actually discover one the others will disappear I think)

The coordinates are relative to your position, But if your at the world origin site, then their the same as the world coordinates. Their in (X,Z,Y) format in meters.

Then as you move around you can use "pos" to find your position in world coordinates and figure how to get to the nearest vendor site.