Me too, - but it would depend on the cost < $80USD per set and you might have a deal.

The only thing I don't know is how large the transformer that converts the low voltage DC to higher voltage AC is required.

There is a small possibility that the existing AC signal used to drive the VFD could be harnessed for this purpose - Rob [from Empeg] mentioned something like 60V (AC) is present on the display circuitry board which might be enough to drive a display board - but you might still want to be able to activate it only during the night to conserve the indiglo panels lifetime [see below].
If not, you'd have to use a small transformer & circuitry and then mount that inside the empeg so that its turned on when the headlights are (relatively easy to do)

This indiglo stuff is really really low-amperage - to give you an idea, down in New Zealand we use 240Volt AC.
You can buy small Indiglo based devices used for nightlights -[for anyone in NZ/Australia these are the HPM Moonglow devices] these are very simply a indiglo planel in plastic connected between the two AC power pins - the AC power drives the indiglo directly using the 50 Hertz AC signal for the on/off thats required (the indiglo panel works like a small light battery - it charges up the electrons (no glow) when the during one half of the AC sine wave when the power is on and the electrons emit light when the AC sine wave is in the other half-wave - so the panel actually turns on and off 50 times a second (for 50Hertz AC), and 60 times a second for 60Hertz AC) and the 240V for the voltage required to get the display planel to light.

They use something like 0.07 watts of power - you can work that out into something like 23 cents of electricty per year to run. [the device cost $14 in local currency and uses 23 cents of power].

This is a very simple and elegant device - [pity they only last for about 1000 'power on' hours before losing their brightness but thats another story!].

Now, to reason for this long dissertation - one day I as testing a solid state 240V relay using the panel as a signal for voltage on and voltage off as it was handy and less bulky than a regular lamp of similar.

But I was very surprised that the panel was dimly lighting even when the power was off [i.e. the solid state relay was not on].

This effect was due to the very tiny leakage current (micro-amps) that leaked through the solid state relay from the 'live' AC input to switched AC out through the light panel wnd flowed out through the other AC pin which wasn't switched..
So, they don't need much power to light up.

The only other comment I'd make about doing this, is that there will be some leakage of light from around the Right button into the regular display window area [the other 3 buttons are mostly surrounded by solid plastic that won't leak much light].

You could cover the light panel with paint to block this light leakage, or come up with some kind of shield to stop it being emitted through the front panel - it would be bright enough to be distracting I think if you didn't.