While I don’t have a Steamdeck or similar, I made myself a relatively portable Mac Mini setup with a wireless mouse and keyboard and a usb-c portable monitor.
Razer Atheris laptop mouse keychron k7 65% wireless/bluetooth keyboard.
The keychron has mac/win mode and came with a few extra keycaps for windows/mac use if it matters. Can be used over bluetooth or by cable. That one has slim profile keycaps. I really enjoy using it. I’ve seen a similar sized keyboard somewhere on amazon that also folds in half longwise to take up less space. Will probably grab one to play with.
The portable one was one I took a chance on Temu. 15” 144hz OLED that I snagged for cheap. Can be powered just on the usbc cable but also had mini hdmi and an extra usbc port. Also has a micro usb port for power if needed too.
The mouse I’ve had forever and is on the smaller side. If I’m feeling for a bigger mouse and plan ahead I also have a MX Master3 for work and a G502 Hero that I normally use at my desktop.