When it comes to electron tubes, it doesn’t get much better than Amperex. One of my rarest tubes is an Amperex 7308 Holland, with the Bugle Boy Logo (made in Canada BC). I have tested a variety of Amperex tubes and the only other companies I feel can hold a candle (for signal path tubes) is Mullard/Philips, Siemens and some GE models.
Looking for something in particular that you can’t find? Contact me and I’ll see if I can help you run it down!