Good Morning!
I have some information I thought I should share in case anyone is interested. In Quebec, we have a travel association for the handicaped. On their website, they have a lot of links, including some to travel agencies around the world (Thailand, Ecuador and South Africa seem great!) that specifically cater to the disabled.
I can't rate any of them (I like to travel independently...)
but I know Keroul has a good reputation.

www.keroul.qc.ca/en/travel-links

Sorry, I'm not good with computers and I don't know how to make an actual link...

Happy Travels!