If you don’t want to splurge, you'll appreciate this Moon River Shell Top. It's a fail-safe choice and a good investment. Another good option is this Asos Shell Top. While the price is rather reasonable, be sure that this product will become a worthy addition to your wardrobe. You might also want to consider this Shell Top. 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 this Paul & Joe Sleeveless Top. While the price is very reasonable, this piece is an easy wardrobe update.