Bought blue LED backlight from Hobby King.
You can install that easily, but then you will have light always on. Of course it is possible to install switch, but then you have to drill hole to transmitter body for the switch. Not big task to do but it also possible to modify orginal LED backlight so that you can configure same from ER9X and use original switches. I chose this path. For this you can find info here.
I also find this vid from Youtube helpful.
|BS170 soldered in place|
|Board removed for LED backlight installation|
|Backlight installed, board back in place, wire from BS170 soldered and wires connected|
|Backlight always on when RUD switch on|