I used this waxed canvas from Fabric.com. For my bag, I used the charcoal and moss colors. The fabric should crinkle and age really nicely, and the leather straps will darken after I've carried it for a while.
If I were going to make another version, I think it would be really luxurious to make the whole bag out of leather or faux leather.
I bought a finishing kit from Klum House, too. They are great kits, including the leather straps and all the hardware so you don't have to track down individual pieces. You can choose the color of the leather (mine is tan) and the rivets (brass).
If you don't want to buy a kit, you could make fabric straps and sew them on instead of using hardware. There is a zipper pocket inside, but you could easily find your own zipper or even add velcro instead. The Oberlin also has a magnetic closure at the top of the bag, but you could just omit it if you don't want to track one down.
There's also a D-ring that I can clip my keys onto. Cute!
I love using this bag to carry our water bottles and snacks when we go to basketball practices or wherever we're going. It looks nice, sophisticated, and like I chose it on purpose. I have some very inexpensive, neon tote bags that I use for groceries, and I used to grab one of those to haul snacks as we were hurrying to leave the house. They looked cheap, like an afterthought, and not look at all stylish. This Oberlin is a nice upgrade to our basketball look.