Emerson Sensi Touch C wire help needed
You just need to pull a C-wire from the AC air handler above the thermostat.  Most smart thermostats power themselves from Rc and C, and only use Rh to signal heating, so your setup is very "typical" and is what they design for.  I have seen a question where someone wanted to pull a C wire from the furnace (power from Rh and C), and that was more complicated and not "supported" by their thermostat, but you should be fine.