There is one Tortollan Seekers Emissary located on each of the Horde and Alliance, Battle for Azeroth islands. The Tortollan Seekers are a neutral faction, available to both the Alliance and the Horde. If venturing into the opposing factions territory, the Tortollan Seekers encampments are not treated as a safe zone, and as such it would be unwise to travel alone if flagged for PvP.
Collector Kojo, Tortollan Seekers Emissary
Collector Kojo is an NPC can be found at both the Scaletrade Post, Zuldazar, on the Horde island of Zandalar. And at the Seekers Vista, Stormsong Valley on the Alliance island of Kul Tiras.
Both factions are able to trade with him at either location, for the Tortollan Seekers reputation rewards. Though he may also be found at various locations, handing out the Tortollan Seekers Shell Game world quests. He can only be traded with at either of his permanent locations.