I have a raspi and a touch screen monitor, I would love to build a very small raspi laptop with a keyboard, I don’t need anything super fancy, just something that would keep everything in his place and be “decently portable” and have some good battery life
Take a look at cyberdeck projects, a lot of them are basically what you’re talking about with holding everything together and batteries for portability. There are lots of guides to build them that cover all the parts you need and how to connect them, which should be a decent jumping-off point for you.