I have three of the window units.
If they plug into a socket, you might be able to find a thermostat they can plug into. If it is 220 Voltage and it likely is, it may be harder to find one. If they’re hardwired, you will need an electrician or a H/C person to get a thermostat wired in.
I would withhold rent until the landlord resolves the issue. Get in contact with city officials, aldermen, city council, health department if the landlord doesn’t respond in a timely manner.