Caster's Satchel: When this item is kept in your inventory you gain the feat: Eschew Materials. mL: 13
This seems like a fairly streamlined and innovative way to aid casters. Many casters, myself included, think there should be a bag for ingredients. This simple item would not be overpowered and no harder to implement than any of the other items that add a simple feat (weapon proficiency, precise-shot, etc)
It wouldn't take a gear slot and would generally make higher level casting less annoying. At level 20 buying 1000 of level 1-9 mats costs no more than one quest's worth in IQ, but it's just annoying.