Thanks for all the suggestions so far! I’m just going to add and clarify a couple of things.
1. I have a folding electric chair with a design that doesn’t have a whole lot going on at the front to be able to attach much to. (I’ll post a photo)
2. Side bags / panniers aren’t really an option - my chair is quite wide as it is, I would struggle with doorways if I added anything.
3. I can’t put anything underneath, partly because of my own physical limitations reaching it from the front and partly because most of the space is taken up with battery.
So I’m thinking any solution kind of has to be limited to my lap or in front of my legs.