For anyone looking for a way to carry your backpack or tote bag on your bike, I have a solution. It may look like an ordinary mailbox, but it is more. The two hooks let you hang your backpack from the top grab handle or sling your tote bag handles over the top to attach them on the other side.
The main part is 3d printed. If anyone would like to try it out, the files are available on maker world:
by Educational_Mud_2793