Have you heard of REMAP?
There are Remap panels all over the country (roughly one per county) and many have members who are model engineers. My panel, for instance (Coventry & Warwickshire), has two. I'm one of them.
I'm pretty certain that your local panel (contact details can be found on the website) will be able to help.
Caution! AD coming up.
If you have the desire, skill, and aptitude to help people by making and/or designing things to help disabled people then please get in touch with your local panel. The panels hold monthly meetings where new cases and progress on existing cases are discussed. There is no commitment on members other than, if you accept a case you should try to finish it. Other panel members will help if required.
Cases can be mundane or very challenging, and can give the little grey cells a great workout.
Oh, you will, of course, need your own workshop.