There aren’t many but you can try Joyful Journey: https://www.accessible-japan.com/travel-agents/specialty-service/joyful-journey/

It could be expensive for a whole trip, but maybe less than bringing someone with you since there wouldn’t be need for flights etc.

I found this company on the accessible Japan’s website and you can hire someone to assist you while you’re in Japan. https://www.accessible-japan.com/taxis/featured/welhire/ I sent them a request from the website and the replied quickly.