here's what Viva Tubes has to say about supply:

As time goes on, some areas are improving while others are worsening. We expect things to stay the same for the foreseeable future. As it stands now, there is typically enough supply to keep the world's amplifiers humming. Choices amongst brands and sub-types will remain touch-and-go but there is no reason to panic. 

Scarce as of March 2023: KT88, KT66, KT77, 6550, 6L6GC, KT120, KT50, KT170, 300B, 2A3, 6L6G, 12AY7, 12DW7 & certain brands of 12AX7.

You may notice that many of these are unavailable on platforms such as Amazon and also from tube vendors as well.

We are well-stocked on all of these types aside from KT120 & KT150. 

See our new Scarce & In-Stock category. 

These are available and are excellent sounding EL34's:

https://sophiaelectric.com/products/pages-se-el34

Sounds like maybe I should plan to sell a bunch of KT88 Gold Lions I haven't used in year.

Yes when many output tubes are made in the USSR .

wuhan you can buy tubes on line ebay .  If your tube type is that scarce then maybe look to buy a nice class A amplifier like a Pass Labs , and a nice tube preamp you would be pretty happy .

Here are two reputable tube suppliers that I have used, and have terrific reputations:

Viva Tubes www.vivatubes.com

Brent Jesse www.audiotubes.com

When I lived in a part of L.A. where a good deal of the movie studios were located, I had maybe three or four nearby retail outlets where I could buy the tubes I required to power my stereo. This was especially important during the days of my 8417 equipped Quicksilver Mono Amps which, for whatever reason, regularly ate tubes and spat 'em out. The tube nightmare came to an end, though, when I bought my 6550 powered Primaluna. Ninety percent of the sound. Five percent of the aggravation.