I checked out a craft book from the library, Make It!, by one of my favorite craft book authors, Jane Bull, and inside was a project where you could make your own jean-bag.
It just so happened that I had a few pairs of old jeans that my friend gave me, so I used one of them to make a bag.
After making the first bag, I had enough material left over to make a second, smaller bag which I use for a pencil case.