Dark Brown Leather Crossbody Bags from shoptiques.com
If you're in a thrifty mode, this Frye Crossbody will fit the bill. It's a foolproof choice, while not very pricey. In this price range, you can also look at this Baggu Cross Body Bag. It's also a popular item and won't break the bank.
If you can afford to spend a little more, we recommend looking at this Anat Marin Crossbody. While the price is very reasonable, this item is an easy wardrobe update.