I think the real problem is that ideally you would want some transparent material and white print, so it shows up properly on a black chassis. Printers just don't do white print, they can do black background and leave the lettering white, but that's not what I'm talking about. The best you can hope for is some kind of yellow.
I wound up getting a really fine white paint marker from an art supply store. Then I very carefully drew out the letters I wanted. It's not quite as crisp as I would like, but it's not aweful either. I tried using a stencil at first but the paint ran underneath the lettering and smeared, so free-hand was necessary.