Baseboard heater powered by a switch, not thermostat
What you need is a line voltage thermostat.  Non--programmable ones are very common. Programmable (digital as you call it) line voltage stats are available but rare. I attached a pic of one that I found. Search for &quot;line voltage thermostat&quot; and you'll find a few.  If you don't care about programability, simple line voltage stats are as common as dirt. Just be sure it's two pole.   I don't know if single pole stats are still available, but for 240, I don't consider them safe.
Not sure what NoSparksPlease was getting at regarding the disconnecting switch (???), I would assume the existing circuit is on a breaker and that would satisfy the code.