Have you asked your local generator/motor rewind shop? KATO had a published procedure many years ago (when they were owned by Reliance Electric) but I can't find a copy. It used a neodymium magnet and outlined identifying north and south poles on both magnets. It worked on a unit at a remote site I worked on but that was many years ago.
SCE had a repair shop in Southern California that for many years did outside repairs, they had equipment and procedures to re-magentize PMG's.
I think EASA has guidelines for it, but not sure of the extent.
Hope that helps, MikeL