Are you looking for a cheap and easy to build Raspberry Pi handheld? Check out the Bumble Berry Pi project which focuses on affordability and simplicity, letting you quickly create a portable cyberdeck perfect for terminal work, scripting, coding, or gaming on the go. Ha! You can have 37 Watt-hour battery that that lasts all day long with with Raspberry Pi 3b+.
https://github.com/samcervantes/bumble-berry-pi?tab=readme-ov-file