Here’s some photos and a video of my mod using an electroluminescent (EL) panel.  Total cost was less than $20.  You can use this method to do other transmitters, like the DX7 or any thing that has an LCD panel for that matter.  I’ve done this mod to a Spektrum DX6i and it works the same way.  Compared to the LED mod this is a lot easier, since you’re not soldering a lot of resistors and LED’s.  It costs a little more but it looks a lot better than the LED mod since there is no bright spots in the corners.

What you need:

EL (electroluminescent) panel
inverter (DC to AC)

Video: