Can’t buy output tubes anywhere except from manufacturers at high prices.

JJ makes the best EL34 and KT88 tubes IMHO.

https://www.eurotubes.com/store/pc/home.asp

Scratch my head too.  I am looking at German made KT88 TK or EL34 TK (Telefunken) too and it seems a few stores carrying them even at BHPhoto.  They last long time.

https://www.bhphotovideo.com/c/product/1502627-REG/telefunken_kt88_tk_vacuum_tube_matched.html/?ap=y&ap=y&smp=y&smp=y&smpm=e_f81_uar&lsft=BI%3A514&gclid=Cj0KCQjwj_ajBhCqARIsAA37s0zrRHi1wPXl_liHFypOcY-XT-A-kjNBCuXHoYDeDo2dg_tAJ12wpE0aAngOEALw_wcB

You can count on

viva tubes

https://www.tubedepot.com/

brent jesse 

as vendors

The JJ El34s & 6CA7s are my go to.

Forget tube gear....there are so many solid state amps that are amazing

I took a look at VIVA tubes and it seems they are fully stocked. I guess I have been looking for tube in all the wrong places! 😂