I've got a bunch of custom labels.
I have some in clear vinyl and others on white vinyl.
I use the clear ones. I carefully write in the wavelength and power class with a permanent marker on the BACK of the sticker so the ink doesn't rub off. See the pictures.
Version 1 doesn't have a space for the wavelength specification. I have some of these in white.
Version 2 does have a space for the wavelength specification. These I only have in clear.
Note that for the clear version, the text will not show up well on a black background, since the text is black.
However, the clear ones look great on silver/chrome.
For the white version, a good permanent marker will stick well enough but will eventually rub off if it's handled a lot.
If you're interested, I can send you a bunch. How does 10 stickers for $1 + postage sound?
If you want the clear ones, I'll even write the numbers you want for you if you'd like. That way you only pay for labels that work out and don't risk ruining some... it can be hard to get the text clean and neat sometimes.