Why not list all shop stands of the planet automatically?
Filterable by item and tint, ordered by either price, quantity or distance.
One click on the entry adds the location of the shop stand too you custom location tracker.
Optionally players can place a location signal in their shop to add some directions on how to reach the shop like: PS Biitula 2nd row west. All shop stands within x distance will display that information on their market board entry.