Items to help AP duration

Ok so obviously creating an item that would stun players would be completely broke and OP, but what about an item that has a passive that adds to AP duration. It would kind of be a counter to an item like Moonflair Spellblade. . Instead of reducing the duration of stuns and other impairments it would increase them. We already of items for counter measure why don't we have items to help players like that. Unless I overlooked the item that has a passive like this if so please let me know, but I spent a good amount of time looking at AP passives and idk where else it would be.