There's no hope of obtaining a tile from 50 years ago. I'm sorry to say that many pros have struggled and given up trying to obtain tile that's only been out of production for a few months, let alone 5 decades.
The best you can do is shop around for either something close, or to install a complimentary or contrasting tile in the area of repair. Hopefully the plumber wasn't the one bashing the wall. Unfortunately, folks from different trades don't really respect where a good or bad place to smash holes would be and repairs are especially challenging.
But on the note of your tile. 50 years is a long time and since repairs are quite difficult to make (I'm assuming this is a mud set wall), perhaps now would be a good time to update your walls with new tile? I know, I know....probably the whole bathroom is the same blue 4x4 tiles...... (I'm hoping they're not, hence the suggestion).
Tonto Goldstein….. but my friends call me Bubba
"The best way to get a bad law repealed is to enforce it strictly"
- Guy on the five