I’m not sure if you saw this, but hopefully it will be an encouragement:

https://www.accessible-japan.com/go-global-traveling-in-japan-with-a-mobility-scooter/

Perhaps the author @gobyscooter can reply.

Ok, so I talked with Frank who runs a ramen tour place. If you book a private tour they can try to meet your needs he said. He is waiting for your email.

Here is the site:

https://www.tokyoramentours.com/contact

I have reached out to my friend who runs an accessible travel agency in Nepal.

Hopefully he’ll get back to me soon.