Kanken totepack
 

Besides being lightweight and stylish, the bag is also made of water-resistant materials. You can even spot-clean it with a damp towel. However, be aware that if you leave it in the rain for too long, the material inside can become damaged.

If you're on a budget, you can choose a Kanken bag that uses vinylon, a synthetic fiber that expands when wet. Vinylon f is water-resistant, light, and able to withstand a variety of conditions.