If you are on a budget, your best bet is this Bucket Bag. It's a terrific product, while not very expensive. In this price range, you can also look at this adidas Backpack. It's a product you'll fall in love with which also doesn't cost a fortune. You might also want to consider this Herschel Rucksack. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.