As far as I can tell, Krzysztof Kaniewski's Piper PA-11 Cub Special is currently the only high wing bush (sorta) plane available for Aerofly FS 4. It is definitely a low and slow aircraft suitable for sightseeing. Note that the airspeed indicator is for MPH and not knots. It is fairly complete although it does not seem to have a functional fuel mixture control but since the FS 4 simulation engine does not use this in calculating engine power output, it's not important. The radio does not work, but that is not required for Aerofly FS 4. You can manually start the engine by using the mouse right button to spin the propeller or you can to assign a shortcut key for "Engine start", requires magnetos on and fuel on, there is no master or battery switch. The "Cold and Dark" and "Right Before Engine Start" tmd presets do not work in that the engine will be running regardless. It is sorta a bush plane but does not have flaps so short field operations may not work out. It does have large tires although not tundra tires. Also, since it only has a 65 hp engine it will have a very slow climb rate at high altitudes (like at Grand Canyon National Park Airport)
You can download it from Krzyszstof Kaniewski's Github repository by clicking on the green "Code" button and select "Download Zip". Once you have extracted the inner pipercub-master folder and put it in your aircraft folder make sure to rename it to just pipercub.
Here are some screenshots in Aerofly FS 4 taken at and around KGCN (Grand Canyon National Park Airport)