Lee,
I always wondered if there is not a huge amount of material of these people published in diaries or so. I read about the existence of a diary by a former headmaster of the Kashima shin-ryu. I think it was published in Japanese.
There are ledgers of the Kito-ryu which I hope one day will be translated and published by someone doing research.
Maybe translating material like that will not be interesting from a commercial point of view but imagine being abel to read about the travels and training of these people.
I traveled around a bit in Europe myself training in jujutsu where I found it. But that was a long time ago. Lot's of memories, some good some bad but those were indeed the days.
Happy landings,
Johan