I used a Cateye AT-100 for a long time. It had a backlight, but it stunk.

It was one of those Electro-Luminescent deals, so the lighting was even, but contrasted with my headlights, it was dim and I really had to zero in on the display and look hard to read the numbers. On top of that, it was on a timer, so one press of the backlight button would get me maybe five seconds of time to read. And lastly, if the batteries were getting stale (this particular model needed a new battery twice a year), it would crash the whole computer. Blooie!

I've since given up on backlights, because even if the thing stayed on for 30 seconds or a minute, I'd probably eventually wreck trying to read it while riding. Plus my helmet lamp has eliminated the need.

Be nice to hook up a small, power-miser LED to a headlight to use as an aux computer light. It could stay on all the time, provice a useful amount of light to make use of the display with a quick glance, and would barely tap the battery. Now that I think of it, it's be pretty easy to rig in line with a typical Nightrider setup that could easily be unplugged when not wanted. Hmmm...