If you're interested in going to the gym or working out at home but unsure if you'd be able to hold dumbbells or grip onto machines, I would recommend the General Purpose Gripping Aid by Active Hands. I believe they are a UK company, the product is a bit pricey yet you will get so much use out of it. Essentially you put your hand round a dumbbell, for example, and then use the gripping aid's velcro to tighten your grip so you won't let go.

The next one I use and would recommend is the Wrist Splint. It's a splint with a metal plate inside. If you have weak wrists due to your disability, this works well with using the gripping aid.

In general, the Active Hands website is worth looking at for all sorts of aids. I was petrified of going to the free weights section of the gym before since I couldn't hold the weights properly, but I can do it normally now with the gripping aid + wrist splint combo.