If you're looking for a thrifty option, this Levi's Backpack will fit the bill. It's a great choice, while not very expensive. In this price range, you can also consider this Backpack. It's also a popular item and won't break the bank. You may also want to look at this Ogio Backpack. This item is not expensive either, but it will make a difference in your wardrobe.
If you can afford to spend a little more, consider choosing this Royce Leather Backpack. While the price is very reasonable, this piece is an easy wardrobe update.