You can still buy the X10 Powerhouse thermostat setback controller [1].

"Mounts on the wall under your thermostat and plugs into an appliance or wall receptacle module. Selector switch (low, medium, and high) 'fools' your thermostat into 'thinking' the room is 5, 10, or 15 degrees F warmer than it really is."

[1] https://thex10shop.com/products/x10-powerhouse-th2807-thermo...