If you can’t spend much, check out this Donni Charm Bandana. It's a terrific item for a good price. You might also want to check out this Rag & Bone Hat. It's a product you'll fall in love with which also doesn't cost a fortune. You may also want to look at this Portolano Beanie. This item is not expensive either, but it will make a difference in your wardrobe.
If you're in a Treat Yo' Self mood, check out this Eric Javits Beret - a great luxury choice. While you're at it, also have a look at this Eugenia Kim Hat. Yes, this item is expensive, but it does not mean it's not worth it. And how about the luxurious Loro Piana Hat? Yolo, right?