I’ve always had trouble with grilling pizza, and I’m always on the lookout for ways to do it easier and better.  I just purchased a new pizza stone with an enamel coating.  It’s designed to go directly on the grill, but keeping consistent temperature is proving to be a problem (if I’m not cooking, it’s getting too hot; If I’m cooking, it gets too cold).  I’ll keep you up to date on how the progress goes.