Where to find out more about "ライダーハウス" / "riders' houses" in Japan?

I just learned of a very interesting kind of minimal budget accommodation in Japan principally for people on bicycle and perhaps motorbike tours called "ライダーハウス" - "riders' houses".

There is an article on the Japanese Wikipedia, but not on the English Wikipedia, and Google Translate tries very hard but doesn't manage to do a perfect job.

Where can I find a resource telling me about these accommodations, especially a resource to help locate them?

For instance, some of the things I'm wondering:

• Are non-bikers welcome too? Hitchhikers for instance?
• Can you normally leave your luggage there while you go exploring, and would that normally be safe?

(I'm not expecting answers here addressing my example questions, only the overall question for sites that would have info including those kinds of answers.)