Most GA aircraft used for travel have autopilots. Even most flight school aircraft used for IFR training have them, at least in my experience in the northeast.
You can buy a full flight director autopilot on a G1000 Cessna 172.
The main reason it can't fully land itself is the lack of autothrottle and FADEC. But some GA planes do have even that. For example the Cirrus Vision (very light jet) is also a GA aircraft and has an emergency function where a passenger can trigger an emergency landing at the closest airport (as well as having a rescue parachute too)
