If you can’t spend much, your best bet is this J.Crew Beanie. It's a wonderful product, while not very pricey. You can also take a look at this Diesel Knitted Hat. It's an item you're bound to love which also doesn't cost the earth. You may also want to look at this Sperry Hat. This item is not expensive either, but it will make a difference in your wardrobe.
If you're looking for something in between pricewise, look no further than this Timberland Hat. This item doesn't cost too much, but absolutely essential in your wardrobe.