Perhaps you can find decals from Micro-Scale that would work. However, you might be the only person knowing the number is not correct, and you may simply ignore the incorrect number.
GARRY
HEARTLAND DIVISION, CB&Q RR
EVERYWHERE LOST; WE HUSTLE OUR CABOOSE FOR YOU
If you know the font (gothic, railroad roman, etc.) it would just be a matter of getting a decal set of numbers the right height.