I totally agree with what TPC YaYa shared. I have degenerative joint disease and I am bone on bone, no discs left. That makes it hard for me to bend and the reacher/grabbers are wonderful tools to have in our pain toolbox.
I have run in to the same issues, finding one strong enough, small enough to carry around and affordable.
To answer your question about a shopping cart design that would be helpful. I would love to see one that makes the bottom section more accessible. If you buy large bundles of paper towels or dog food it is so hard to put them on the bottom part and even harder to get them out when you are checking out.
I have no idea how the shopping cart could be changed to make that bottom section more user friendly for people living with pain but I would so happy if someone does.
Good luck with your project and pain.
Noki4