Not a dedicated met course, but a useful advance on the basic training, whilst you are still in the PPL stage of your flying career: Irv Lee's PPL masterclasses. The weather section is particularly clear and helpful and, although not aimed at the commercial flyer, can add significantly to your understanding of concepts which may be left somewhat hazy at PPL level (they were with me, anyway). Lots of other good stuff as well as weather. Good luck with your continued training.