Musicians Roadhouse

FWIW/PSA: you can get 6N4J chinese preamp tubes with square-getters (the tubes the amp came with) for like $8 each on Aliexpress. Although it might take a couple weeks to ship to the US. They are at the other end of the 12AX7 spectrum as the JJs.

Well damn, I just checked and they have dried up a LOT. There were a bunch of listings a few weeks ago. If you've seen others 'selling their stash' of these then they might be these. That happened on another forum.