Adventurer tier magic cloak-slot item (+1 to PD.) This and other magic items I've created are collected together in the attached PDF.
Quiver of ______: This quiver takes up the same chakra as a cloak or cape would, so it's one or the other. As long as there are arrows in it (or stones, or throwing knives, or whatever,) it will generate 2 arrows (or stones, blah blah blah...) of the quiver's type daily. If they aren't used they will be stored in the quiver cumulatively, to a maximum of 10. The arrows can be used at any time, but must be declared before the attack roll.
Quirk: Variable. While magical ammunition doesn't carry with it a quirk, the magical quiver does. The quirk should be tailored to suit the type of ammunition it generates.