A pocket in a backpack is a common thing. How about a backpack in your pocket? A folding backpack will not take up much space in the trunk, and if necessary, will give an additional 20 liters of volume.
Roomy backapck that can be folded into a compact bag.
A loop of non-woven material on a steel button enables you to fasten a folded backpackto the belt loop orcarabiner ring on the backpack or bag.
Ripstop fabric is the perfect combination of strength and lightness.