If you're not planning on spending much, this Brixton Hat will fit the bill. It's a great choice, while not very pricey. Another strong contender for your wardrobe is this Club Monaco Hat. While the price of this piece is not too high, it will definitely attract a lot of attention.
If you're a bargain hunter, consider buying this Rag & Bone Beanie Hat. While the price is very reasonable, this product is an easy wardrobe update.
If you have enough to afford it, then you absolutely must check out this Eugenia Kim Beanie Hat. This product seems costly, but it's well worth it.