Canvas Backpack

Canvas Backpacks from Urban Outfitters

If you're not planning on spending much, this Backpack will fit the bill. It's a popular choice, while not very costly. In this price range, you can also take a look at this BDG Backpack. It's also a popular item and won't break the bank. You might also want to consider this JanSport Backpack. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.