For something in the middle of the price range, why not take a look at this MCM Backpack. While the price is very reasonable, this item is an easy wardrobe update. It's also worth looking at this Meli-Melo Backpack. This item is extremely popular and, just as importantly, not very expensive. Take a look at this Milly Backpack too! Great value for your money.
If you can afford to splurge, then you absolutely must check out this MCM Backpack. This product seems costly, but it's worth it.