If you're not planning on spending much, your best bet is this Beanie. It's a wonderful item, while not very costly. In this price range, you can also consider this Collection XIIX Knitted Hat. It's also a popular item and won't break the bank. You might also want to consider this Hype Beanie. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you're looking at it like an investment piece, then you won't be disappointed if you check out this Jennifer Behr Hat. It's a costly but smart option. While you're at it, also have a look at this No.21 Beanie Hat. Yes, this item is expensive, but it does not mean it's not worth it. And how about the luxurious Markus Lupfer Beanie? Yolo, right?