Are 6as7g tubes becomming harder to find?

Just look on Ebay. Search 6N13S and 6AS7G, plenty of Eastern European sellers. I retubed my M60's for about $200 for 24 tubes.
Shipping took about 2 weeks. Not one failure, though my amps are the Mark III versions.

I believe Ralph has a couple sources for 6AS7G and tests the tubes before shipping with his amps and/or individually.

Call or email him for specifics.

Dealer disclaimer.

Hiendmmoe, the importer of Russian 6AS7Gs got to be too difficult to deal with. We saw the price double in a 3 month period several times.

The Chinese 6AS7G has been in production for the same length of time (since the early 1960s). All the Chinese ask is 'how many do you want?' -no games. They are in current production there FWIW.

Try conusaudio.com; Russian 6H13C @ $15