Easy to make with recyclables you may already have!
Step 1: Create the backpack from cardboard and webbing!
Build arm straps like a back pack. Through the top and around to the side. I used old backpack webbing and just stapled it in place to create arm holes! I added a strap across the chest that is stapled to the arm loops and buckles in front. It's like the rocket stabilizers. :)
You could use old webbing, shoelaces, or rope, braided yarn, twill tape...anything you have on hand!