Hi Voxman,
i can just speak for germany.
The last remaining online tube-dealer is BTB (
https://btb-elektronik.de/en/start-en/).
I don't ask "Jan first". (german insider-joke) ;-))
If you need some "specials" (triodes, rectifiers, stabilizers) maybe i can help you.
In my stock i have so many tubes i can't use in my life. :-)
Also i'm in a radio-collector-club and have an offer from a dear member
for six WE437A (NOS, consecutive Ser.-#!!).
If i just had that money...... B-(
Good luck and best regards