tv screen in rear view mirror

I have a mustang convertible, have been a mustang owner for many years......in this vehicle i have the rear view tv so when i back up i can see if there is anything behind me........however when i put my car in reverse and look in the mirror it is very difficult to see what is viewed.....i need to hold my hand over the mirror to shield the sun and light , however that is unsafe .....what you need to come up with is a small shield which will sit on top of the left corner of your mirror and shield the sun and light.........let me know if this is something that can be done.....if so i would like to have one on my car...........