There are some NUC like systems available, but they are primarily for embedded/industrial use. On Alibaba such devices have their own category https://www.alibaba.com/showroom/battery-powered-mini-pc.htm...

Thank you, this looks like the kind of thing I was looking for (even of I'd prefer one was made by a company I'd heard of)

If you can get by with suspend to disk, any of the nuc like thing should work. The Intel compute module PC on a stick from a couple years ago would make an easy to carry device, although I don't know if there's been any of those with updated processors.

Curious about your use case.

Depending on what you are after a Raspberry Pi is cream enough to duplicate or operate with a battery.

https://howchoo.com/pi/raspberry-pi-gadget-mode

Is there some reason you don't want a screen and keyboard? If it's just for the sake of portability, you can get a GPD Micro PC - it has a screen and keyboard but it's hardly bigger than a NUC.

Why with a battery? You will need a power supply to power the monitor anyway, so I would just use an Intel NUC or any other mini PC.

I'd like to know if you use your machines for any specific applications, or if you just surf the web.

why not plug the mac mini into a battery? remove the psu and get a 12v battery.

why would you want that though? you want it on in your bag as you’re traveling? If you can power a screen, then you can power the mm. It doesn’t make sense and the mm boot instantly now