To find an airplane light-sport aircraft DPE (Designated Pilot Examiner) to perform a checkride (practical test) simply go to the FAA website listing and finding an examiner in your area. FAA Designated Pilot Examiner List
Many times the instructor who recommends you for a checkride will suggest an examiner. This is the best situation if the recommending instructor and the DPE have worked together before. The instructor typically will make certain you are prepared for your checkride because he will not want to recommend an applicant for a checkride only to have that applicant fail.