If you're after a thrifty option, consider buying this Forever 21 Tank. It's a wonderful product for a good price. In this price range, you can also take a look at this Alexander Wang Tank. It's an item you're bound to love which also doesn't cost the earth. You might also want to consider this J.Crew Tank. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.
If you can afford to spend a little more, look no further than this Lanvin Tank. This item doesn't cost too much, but absolutely deserves a spot in your wardrobe.
If you have enough to afford it, then what you're looking for is this Polo Ralph Lauren Tank. It's more expensive but worth your money.