I once asked a guy at a Gamestop if I could buy a Forza case. He just gave it to me and said to have a good day.
Another time I had shown slight disdain about a sticker mark so without even asking he took me over the the Wii U section and found a nicer case then took the time to pretty that one up.
When I was in another used game shop, they had a section that sold just manuals and cases separately. They also sold full games with and without the original art. I just needed a case/manual to a PS1 game and asked to buy just that and not the game. The guy working there basically told me to shove it. All the shops of that local chain are closed now.