Generally speaking, the overall process of backpack customization is as below:
Making Backpack samples > Making Cutting Die>Cutting materials>Printing Patterns or Logo>Sewing>QC>Packing>Delivery.
Military Backpacks share same producing process. as below picture:

There is also wide custom options for military backpacks: LOGO, Color, Fabric,Style. as blow picture:
Custom made tactical backpack with Small MOQ: