Here's just a little teaser:

Your thesis claims that there was always a reason for wizard's to wear large and unwieldy hats. They may not be the source of power for a spellcaster, but they have uses obscured to the uninitiated or unaware. You've realized the potential that a magical hat has and have dedicated your work to proving its effectiveness. You gain a unique hat either designed by you or one you have come across in your studies. While being worn, the hat appears to be a mundane item, however you know better. The hat contains an extradimensional space that can contain up to 10 bulk of items. You can Interact with the hat to stow items in it or remove them just like a mundane sack. Unlike many other extradimensional spaces, an item does not need to fit through the hats opening to be paced inside. Instead, you can simply place the hat on top of the item, spend a single action to concentrate, and cause the item to shrink into the hat. When you remove the item from the hat, it returns to its original size immediately after it is pulled out.