If contacting American Technology Components proves fruitless you can have a label maker make some up custom for you.
Contact Link: https://www.atcomp.com/contact
What I did for my switches that have worn off letters was used my P-Touch Label maker with Clear Labels and played around with the font and size until I got something similar then trimmed it down to size and just stuck it on top. Still working find after a year.
We are all curious what you find out when talking with American Technology. If you don't mind posting what you find out and the results of what you end up doing.