Need a cheap, battery-powered camera with built-in recording memory?

Question

CCTV

You need to put it in an elevator to determine who is a hooligan there, black and white will do, put it in and in a few days look at the recording from the flash drive.
Tell me the simplest and most affordable models.

Answer 1

Any DVR from the car.

Answer 2

You can do this or this, plus any capacious power bank.
or this is a plus , this is the collective farm power supply 12v.
or a car recorder with a motion recording function, for example, with 12v collective farm power.
Problem number 1 - where to hide all this in the elevator.
Problem number 2 - how to power all this with autonomy in a few days.
Problem number 3 - buying Chinese microregistrators, as well as conducting covert filming - at least in Russia is a criminal offense. The risk is quite formal, but it must be taken into account.