Yes, the EVO frame arm is compatible with S800 and you can purchase them from your local dealer.

Stator Size: 41×14mm
KV Value: 400rpm/V
Max Power: 500W
Weight (with Cooling Fan): 158g

S800 EVO has a strengthened and rigid frame structure, strong and stable power system and also an efficient and abundant power reserve. It has a standard configuration including retractable landing gear, folding propellers, folding GPS bracket and the high performance Vibration Absorber Kit.
If you want to get a smoother and more stable flight experience, you can install the IMU module on the IMU mounting plate. Once you have installed it on the IMU mounting plate, you have to turn down the basic gain value, in order to prevent the control oscillation, due to the attitude response delay. For recommended gain values, please refer to the latest WKM user manual.
The mark on the propeller cover is for you to check whether there is a loose screw before or after your flight.
Fasten it as tight as possible, but make sure that the propellers can be unfolded smoothly when you start the motors. If they are too loose or too tight they could give excessive vibration.