Grey Open Cardigans from 6pm.com
If you're on a thrifty mission, your best bet is this Bobeau Open Cardigan. It's a great piece, while not very expensive. In this price range, you can also check out this 525 America Open Cardigan. It's also a popular item and won't break the bank. You might also want to consider this Open Cardigan. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you're looking for something in between pricewise, consider choosing this BCBGMAXAZRIA Open Cardigan. While the price is very reasonable, this item is an easy wardrobe update.