Have you been inside Sin yet? If so, then Elio, the 9th cactuar should be on the DECK of the airship. If you don't remember how to get there, just keep going to the right inside the ship, and when u hit the other save sphere with the big stairs, just go up the stairs and to the end of the room, the back, there will be an elevator leading to the Deck of the ship,. Walk to the end and you should get a little movie of him dancing. For the last cactuar, just go back to the stone, and he'll pop out when u put the 9th sphere in, or at least he did for me.
