Staples does the image reversing on their copier. All you do is bring them the gauge faces, lay `em on the bed, reverse the image, and print it out on semi-gloss paper. If you do it right, it cost less than $2 a set if I remember correctly.
I would imagine that you could also feed the images into your computer and photoshop the numerals and design too....
As you can see, I've given this alot ot thought :-s