PerilsofP, adaptive clothing is clothing designed to help people with disabilities. For example, my grandson has shoes that look like sneakers that tie, but there is a zipper on top that runs around it, so you just unzip that and slip the shoe on his feet, and zip it up again.
He also has a sort of heavy fleece cloak that I made him for cold weather that is high in the back but long in front so it covers him in his wheelchair but doesn't bunch up in back and made it uncomfortable for him. it also zips up in the front so it's easy to get on. Coats are very difficult in wheelchairs and the cloak is very helpful. But this is for a 13 year old boy who is almost totally immobile and can't really move his limbs. So it might be different for your friend.
Without knowing what he needs, though, I would be hesitant to recommend something like that. Do you know the extent of his disability? I'm assuming he is an adult, since you mentioned he uses an electric wheelchair. Is there anyone near to him (friend, relative) that you could reach out to and ask?
ETA: Here is one website that shows you some different types of adaptive clothing. For example, there are shirts that are easy to take on and off, with a quick release in back. pants with size zippers for easy removal, and the shows I was talking about. It might help to give you some ideas.
Etsy has a lot of these types of shops as well. There are some practical ideas for the chair as well, like hanging bags that hold books, a phone, etc., and so on.