If you don't want to make a bag you can modify any tote you've got by simply moving the handles from the middle of the bag to the corners and reattaching them by any method that works for you.
Here's a bag that I sewed from fabric scraps, buttons and a small piece of webbing:
There's only one number to remember: 12 inches. It's the finished dimension of the bag (both height and width) and it's the length of the straps before they're folded in half and attached to the corners of the bag.
This bag is different on each side because I was using up all of the scraps of fabric that I had sitting around the house.
I'll probably add more buttons, beads and embroidery as I come across odds and ends around the house so it gets a bit more interesting all of the time.