The Penkesu computer is a homebrew handheld PC ideal for writers and coders

The Penkesu, created by Penk Chen, is a handheld PC no larger than its keyboard, made as minimal as possible with standard-size low-profile keycaps. Best of all, you can make one yourself from parts, most of them easily available, though 3D-printing is needed for the case itself.

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.

If that grid keyboard layout is just not going to do it for you, Vortex makes a relatively inexpensive 40% model with a standard staggered layout, though you'll surely have to remodel the case some.