I would say it would not be considered "normal" for a mag to malfunction at less then 200 miles, but I would say it is quite possible. Pretty simple ignition system on these engines...so if you have replaced two out of the three possible culprits in the system and still have no fire, then it is quite possible that your mag has failed.
I have not really seen any aftermarket magnetos for upgrade although there may be, but I have read a few threads an articles detailing how to wind your own for better performance. Other then that I believe the more simple route is just to order another mag and hope you get a better one. Quality control on some of these electrical components is probably not the most uniform, but I have gotten hundreds of miles out of stock mags without issue.