For something in the middle of the price range, why not look at this Letarte Bikini Top. While the price is very reasonable, this product is an easy wardrobe update.
If you're not a thrifty type, then you absolutely must check out this Herve Leger Bikini Top. This item seems pricey, but it's worth it. While you're at it, also have a look at this Michael Kors Bikini Top. Yes, this item is expensive, but it does not mean it's not worth it.