Book of Storing
Wondrous Item,
Uncommon
(requires attunement; cost 350 gp)
Crafting Components
Beautiful leather bound tome, scroll of major image
After you attune to this 1-foot square 6-inch thick book it hides its true nature to anybody else, appearing to be a mundane diary. When you open it however, the book reveals a Tiny storage compartment.
The storage space is the same size as the book, and because this item doesn’t function as a pocket dimension it can be safely used to store such items (such as a portable hole ).
Source