I would take a cue from the Uncharted series and focus on finding a place as much as an object. Atlantis, El Dorado, Shangri-La...
It might be too similar thematically to the Holy Grail but a search for the Fountain of Youth could be an interesting adventure.
It might be too similar thematically to the Holy Grail but a search for the Fountain of Youth could be an interesting adventure.