Trial and Error, the cheapest/fastest way to learn.
Super sneaky spy sublimated dyed glow in the dark lettering. Flash an ultraviolet desk lamp and bam, those hidden letters/symbols shine and it is more intrigue than an illuminated with the lights off, suddenly turned on . . (substitute easy to wear off invisible black light reactive stuff you drew on yourself . .)
A printout layout chart, etc. is another cheap alternative. Opening a jpg of the layout is a greener alternative.
On a more serious note, I think that's a solid idea. Other than talking to a key manufacturer, I don't know of an existing alternative, though.
I had a thought, they make keyboard stickers, just get a pack and stick them on the sides. You don't hit the sides, so they aren't going to wear.