I have a new set of the MTH Premier Santa F7's that just came out. Both my A units are the same road number. I wonder if anyone has any good tips on what to use to change the lighted number boards on the nose? I know they're just an insert. MTH's website doesn't show the number boards in the parts breakdown. I am going to call MTH and see if they sell replacement numbers.
You can reverse print them on paper and glue the paper to a piece of plastic. I use Evans Hobby Cal instead of paper as it takes a sharper image with denser black and will adhere to plastic without additional adhesive.
Hobby cal is apparently NLA. Evans designs, the LED guy, used to offer it. Its a decal paper. Its too thick to use on trains but good for buildings or applications like this. Its white paper and the white will turn clear if coated with a solvent varnish.