I think the DAN Case will be my next case. It can fit a full-length GPU and fits in a normal backpack. https://dan-cases.com/
Random related thought: Someone gave me an old Macbook Air yesterday, that isnt working right, but the screen, keyboard and touchpad is working fine. Wonder if I could modify it, so it just acts as an external screen, keyboard and mouse for the small PC?!!? Should be doable..