if you're in a thrifty mood, your best bet is this Milly Tank. It's a great product, while not very costly. Another smart option is this BB Dakota Tank. While the price is competitive, be sure that this product will become a wonderful addition to your wardrobe.
If you can afford to spend a little more, why not consider this Joie Tank. While the price is very reasonable, this product is an easy wardrobe update. Why not also check out this Samantha Pleet Tank. It's an attractive option both price and quality-wise. Check out this Club Monaco Tank too! Great value for your money.