If you are on a limited budget, consider this Susina Rollneck. It's a popular product for a good price. Another good option is this Turtleneck. While the price is not too high, be sure that this item will become a valuable addition to your wardrobe.
If you're looking for something in between pricewise, opt for this Love Moschino Turtleneck. While the price is very reasonable, this piece is an easy wardrobe update.