Smallest that would fit a battery and a Heltec v4.
Live in a fairly small town in the southeast US but the local Amateur Radio club has a Meshtastic radio on a tall building in town and I was immediately able to see ~20 nodes and had 5 people talking in LongFast.
Wish I could have an outdoor pole mounted base station, but living in an apartment makes it hard. It seems to work okay on my 3rd floor windowsill though!
Link to case model: https://www.printables.com/model/1519914-heltec-lora-32-v4v3-pocket-pager-case/files
Someone really dedicated to finding you could theoretically analyze a series of random points over time and extrapolate the radius and center of the circle, effectively locating your radio
It honestly wouldn’t be that complicated after collecting enough random points