Look up “field monitor” on Amazon, there are some for under $100 (usually 7” 720p native res panels). A lot of them have 1/4” or 3/8” stud mounts for mounting as well, some can accept common batteries like LP-E6 for portable usage, some are touchscreens with USB etc etc. Pretty hacker-friendly hardware. I keep a couple around for pis and terminal access to servers.
