You just need some cardboard and some cutter. IT'S FREE!
This is a small personal project that was basically made to solve the issue of working on my laptop for a long time. My neck started to hurt and ergonomically wasn't good for my back. So after some quick sketches, I modeled a 3D version (download it here) of what I thought was good and then print the shape to get it working. Just an afternoon project that goes inside my backpack everywhere I go. Light, strong and back saver! But yes, you also have to carry your keyboard and mouse :)
You can find some more cool projects in my website: agustincastineira.com