you can create your own backlight for any transmitter
the cost of this project is less then 50rs but little time consuming,if you got some spare time you can DIY it in less then 2hrs
lets do this

Materials:
1) acrylic sheet 4mm (size is depending on your Tx screen in my case 88mm*43mm) turnigy 9x
2)RGB led strip
3) some thin wires 2mm
4)dip switch
5)sand paper for sanding acrylic surface
6)some tools

measure the size of your TX screen and cut the acrylic sheet to suit your tx screen size
after cutting sand out any rough surfaces
remove one side of the protective film of acrylic

the HK backlight is of straight acrylic with side leds and bottom reflective surface
but the drawback of this is lot of light pass through the sides
so you need an angled surface to reflect the light towards the screen
below pics explains a lot

start sanding one side of the acrylic surface
it can be easily done by rubbing the surface againest a rough surface and later sand with sand paper
the sanding should be done as shown in the pics

after sanding prep the led strip for soldering
many of the led strips works on 12v supply and no need of external resistance to limit the current
cut a section of led strip that consists of three RGB leds and three resistors
cut the individual leds and resistors of the section

stick the leds to the thick side of the acrylic in same orientation using CA (feviquick)

start soldering resistors to the leds
you can check the position of resistors and connections using other section of led strip

you should solder using a low wattage soldering iron
mine is 25w and the leds cant withstand such heat
after messing lot of leds the final soldering is

after checking the working condition of the leds you can connect the wires
solder some dark wire for the positive and light one for the negative
after that end up with with 4 connectors one for positive three for negative

some colors using different combinations of the three negative wires

some more

now the transmitter part
carefully open the tx back cover

remove the main pcb and clean out the surface of the screen
secure the leds with some hot glue
remove the protective film of the acrylic and place the shiny side of the back light on the screen ( sanded side should face towards you)

gently remove the foam from the back of main pcb

place the reflective material on the back light
any thick white paper will do the job
place the main pcb on the back light and observe for the gap
if you see any space between main pcb and the back light place a thin foam sheet to fill out the gap
mine had no space for the foam so i fixed the main pcb directly

make sure that everything is working and check with external power
after that check for the positive and negative in the the TX
for my flysky 9x

connect the positive directly to the back light
you need 4 way dip switch to change the colors
place the dip switch on the tx wherever you need
i decided to place the switch near the antenna

drill a hole and pass the four wires through it

great work pratap

@girish thanks

bend the legs of dip switch and solder the four legs together

nice

if only i could patent my idea of a backlight 

http://www.rcindia.org/radios-and-receivers/backlight-install-for-spektrum-dx7s/new/#new

@vishal started this project two months back and bit busy so couldn't post in the fourm

solder the four wires to the four unsoldered legs of the dip switch

i finished off mine more than a year ago 

http://www.rcindia.org/radios-and-receivers/avionic-rcb7x-review/25/