I had printed a bag hook (https://www.printables.com/model/1453-desk-bag-hook) for my son a while back and it worked really well.

But its kinda big and no simple way to attach it to my backpack.
So I came up with this to use in my office.   It has a hole so you can tie a rope off so you can permanently have it on the backpack.

To be strong make sure to add a couple of perimeters and print it 50% gyroid in fill.