No such thing as an Examiner rating! There is no stipulation that an Examiner Authorisation needs a commercial licence however, you cannot be remunerated on a PPL, other than as a grandfather right that you currently enjoy for your instructing however, that right will not extend to examining if you did not do it pre JAA. Why would anyone want to spend lots of money becoming an examiner if you can't recover the cost?
JAR-FCL 2.420 Examiners shall hold a licence and rating at least equal to the licence or rating for which they are authorised to conduct skill tests or proficiency checks..