You can find one in Germany if that’s an option for you:
https://www.akkordeon-maurer.de/verkauf.asp?id=2&id2=10&lang=1
This is a well-established repair shop and store for accordions and related instruments including vintage melodicas. It’s also a good source for Claviettas. They test and tune all instruments before selling them.
To translate the German text I recommend (copy and paste the text to translate):