Backpack of Concealment
This plain leather backpack is covered with pockets big and small.
Wondrous Item 520 gp
This backpack can conceal any one object placed within it from a physical search. Any creature other than the one that placed the item in the backpack cannot find the object. If the backpack is destroyed, the object falls from its remains.
Published in Mordenkainen's Magnificent Emporium, page(s) 80.