Why can I not find a 120V programmable 2-pole thermostat
The problem with starting from a fallacy is that it leads no-where useful.


  The difference between 1 vs. 2 poles involves whether or not the thermostat can truly, completely cut power or not. With 2 poles, all power to the heater can be cut. With 1, the "off setting" is really a very-lower power setting.


Patently false. Incorrect, wrong, and ignorant. A single pole switch. relay, or thermostat will cut all power to a 120V or 240V heater - the reason we don't use single poles for 240V heaters in the USA/Canada power system is only for an extra degree of safety, not because any power magically makes it through an open switch. If you use a single pole switch on a 240V heater in our system, the "switched off" heater would be at 120V relative to ground - it would still be firmly off, not dissipating any power, as no current is flowing, but it would present a slightly higher shock potential, or a much higher shock potential if someone were to open up its connections (believing it to be "off" at the thermostat) without shutting off the breaker for the circuit.

The reason you cannot find the item you seek is that your starting assumptions are incorrect, and there is no need for, and thus no market for, a 120V two-pole thermostat. Properly connected, the hot line is switched, and the neutral is not, and when the switch is open the entire heater is at approximately 0 volts with respect to ground, and thus there is no safety advantage to using a two-pole switch on a 120V heater.

This makes me think of James Thurber's Grandmother who was sure that electricity was leaking out of switched-on sockets with no bulbs in them...