Choosito offers users the opportunity to refine search results by reading level. This will not be as specific as a lexile level but can be separated by early readers, emerging readers, fluent readers, and advanced readers. You also have the ability to refine search results by subject area for more specific and relevant results.
Choosito does require you to sign up in order to use it but the sign up is quick and easy. They will give you a one month free subscription to their more advanced account type. With the trial subscription I have been able to set up a class in choosito to allow my students to use it as well.