This ordinary-looking backpack is surprisingly light.
Wondrous Item 5,000 gp
This backpack can hold up to 1,000 pounds in weight or 100 cubic feet in volume, but it always weighs only 1 pound.
Drawing an item from the backpack is a minor action.
Published in Player's Handbook, page(s) 254, Dungeon Master's Kit, page(s) 269.