It's not an object, it's something that you're able to do. Here... watch.

[Minako sets her watch down on the table, so the view now shows most of her bedroom. She steps into the middle of the room and concentrates.] Persona!

[the ground beneath her glows blue and moment later, Orpheus appears above her.] ...This is Orpheus, my Persona. You just have to learn how to call yours.