Stick two side-by-side. Folds flat for transport!
This is basically the idea I had. Get two monitors that aren't huuuuge (which, smaller displays are practically at a premium these days) and put them together on a dual-monitor VESA arm. You can fold them "into" each other for transport and carry them by the arm. You might not be able to pack them away into some kind of luggage, but they shouldn't be super hard for most folks to carry in one hand. Just make sure you'll have a desk/table you can clamp onto.