Grey Beanies from Bloomingdale's
If you're in a thrifty mode, your best bet is this Hat. It's a terrific piece, while not very costly. Also look at this Bloomingdale's Beanie Hat. It's a product you'll love which also doesn't cost the earth.
If you want to treat yourself, then you absolutely must check out this Moncler Beanie Hat. This item seems expensive, but it's worth it.