I had my mirror smashed by another car coming too close. The mirror back can be purchased from your local dealer but the big cost is having it painted to match the car mine cost 75 quid!! you can imagine I was not happy. You might be luck if you can get one from a breakers and repaint it your self or like me get it sprayed. My car is agean blue metalic!! n o surprises there with my log in name.
The mirror back clips into place it take seconds to fit, you can get the motor and heated element mirror from the dealer if you need it not expensive.