We (Olark YC S09) are in the process of building out a fully accessible platform for realtime communication (live chat, bots/automations) for both agents and visitors, and regularly work with folks to help our team test and improve our work -- it's still early days Progress Not Perfection :).

I am definitely interesting in talking, you can apply as a tester here: https://www.olark.com/ada-accessible-live-chat

And you can ping me personally on Linkedin if you want to chat more. (https://www.linkedin.com/in/bencongleton)

We work with both individuals often as contractors, and agencies as well.

You might want to talk to the folks at lighthouse SF, they do consulting for a lot of tech companies, and have a matching program, I am actually going to be at their offices Thursday, so I can follow up with best way to get in touch, but I'd assume the emails on the below link will get you what you need. https://lighthouse-sf.org/programs/access-technology/

And we've also worked with Fable who manages engagements like what you are looking for: https://makeitfable.com/community/