Make Your Own Pocket Computer

Penk?su (Japanese: ?????) is a retro-style handheld device powered by a Raspberry Pi Zero 2 W, a 7.9 inch widescreen display (400 x 1280 resolution), and a 48-keys ortholinear mechanical keyboard... More here.

If you want to build your own, go here. If I had the time I would give this a go, and the technical knowledge and patience and commitment. I have none of those.