Brian my Setra had one from the factory, and I've seen them that plug into a cigarette lighter at auto parts places! But if it was me I'd pull the dash panel and fix the bad bulbs or bad grounds on the guages where you can see them good all the time, not just when you have the flex light on! (lights like that sometime get pretty annoying at night in a bus as there is sooo much glass to reflect off from and back to you at the weirdest angles & times! BK
Briefly stated, at low light leves, the eye is more sensitive to blue-greens, so gauges lit with these colors are easier to see. The downside is that looking at the blue-green also affects the sensitivity of your eyes more, so that when you look back out at the dark road, your eyes have to re-adjust more. With red light, your night vision is far less affected.
I found one that will be usnig for the passenger, on a flexible gooseneck. Low voltage so I can hook it direcdtly to my DC suppy. Lowes had it.