If you're looking for an item in the middle of the price range, take a look at this Stella McCartney Crossbody Bag. While the price is very reasonable, this piece is an easy wardrobe update.
If you're willing to splurge, then you won't be disappointed if you check out this Chloé Crossbody Bag. It's an expensive but smart option. While you're at it, also have a look at this Jimmy Choo Crossbody Bag. Yes, this item is expensive, but it does not mean it's not worth it.