Non programmable convector idea


I’m looking for a smart solution to cut on my electricity bill

On my basement, I have convector heater with programmable thermostat on the walls (non smart), but on my first floor, all my convector heater have built-in thermostat and they are non programmable (they are high end convector so changing them is not an option)

I know I can by pass the built-in thermostat and run a new cable in the wall to a new programmable
thermostat, but that seem to be a pretty good/hard/long job

I was thinking, is there a smart outlet that I could plug on the current cable, to cut the electricity to the convector when we leave the house? Or a smart button clicker to install on the built-in thermostat to drop the temperature?

If you have other ideas, let me know