A Modular 2 section insert from the M-Tac brand will help rationally organize the space in your backpack or bag.

Made of modern polymer composite, which has exceptional abrasion resistance, strength, and durability. Elastic bands are designed to hold a flashlight, multi-tool, knife, gas can, and other useful items. Attaches to the inside walls of a backpack or bag with Velcro velcro. A lightweight and the compact modular insert is useful for those who like to keep their EDC kit in order.