If you're a budget-conscious shopper, your best bet is this Zella Tank. It's a wonderful item, while not very costly. Another strong contender for your wardrobe is this Nic+Zoe Tank. While the price of this product is not too high, it will definitely attract a lot of attention. You might also want to consider this Lush Tank. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you're looking for something in between pricewise, you're in luck with this Current/Elliott Tank in stock and waiting for you. You are bound to love this piece. You can also look at this Misook Tank. It's an attractive option both price and quality-wise. Check out this Helmut Lang Tank too! Great value for your money.