The supplier I use in Europe (Brussels) is Halfin. They have in storage warehouses all kinds of interesting valve types and CRT's and semiconductors and can usually acquire the most obscure items I need too. I have been dealing with them for well over a decade if not 20 years. I have not seen them mentioned much on restoration websites, so its probably about time I "let the cat out of the bag". I found them a long time ago searching for vintage CRT's:
https://halfin.com