Found at pottery merchants.
Plane of Knowledge
Elisha Dirtyshoes @ 394, 945, -91, Northern trader building
Sculptor Radee @ -290, 790
Crescent Reach
Potter Subira @ -1209, -1482, 13, on second level, sitting next to hut in front of Forge of Nokk
Gulf of Gunthak
Cadale Brohat @ 1516, -244, 4, in the lighthouse