Play a clone of Tetris
Tetris has suggested efficacy in attenuating development or severity of trauma and it seems to have a beneficial ongoing cognitive effect also.
Don’t get Tetris™️, get a good paid version that lets you buy it and doesn’t show ads or track you after buying.
I find it cumbersome to ensure they stay charged. I already have to manage that with my phone and this way I can use it whenever the occasion arises. It does feel nicer tactile-wise tho with a gameboy
Edit: have a DS
MyBoy is a good GameBoy emulator, best of both worlds.
If you want the best of all three worlds, Lemuroid is an emulator based on Libretro, it can emulate a ton of different platforms including Gameboy. It’s free & open-source, unlike MyBoy.
Then you have everything, even the good battery life to don’t make this an issue at all.
(I’m very biased for this handheld, which I use even more than my Switch and PS4).