I'd say whichever slot you want, really.
There isn't really a true rule on how body slot affinity is handled and so it falls to whatever makes sense. Many magic properties can be placed without penalty on more than one kind of body slot as well.
For maneuver magic items, the ToB pretty much made it clear that the disciplines' linked magic item vary so much in style that matters little where they go.
A ring always felt like an always suitable place to put that kind of ability.
Ring, Hand (one glove that uses both hands' item slot), Arms work too for the same reason... maybe Throat for a nuclear-dragon-made variant or even the nuclear chest-eye. One could also argue in the favor of the Shoulder slot because of the space-vision cloak or even Head for the tattered ribbon. She also has special footwear... When it comes to Utsuho and distinctive gear, the options abound.