Tube vendors.

Brent @ AudioTubes. Great deals on NOS, but some are not so NOS but given the pricing, ridiculously good value.

eBay but ya gots to know what you're doing.

Brent Jessee Recording for NOS signal tubes and TC Tubes, for outputs.                       You already mentioned Kevin/Upscale, with whom I've never been disappointed, either.                                                                                                                                                     Then: there's this ebay seller, in Germany, with whom I've dealt multiple times, in the past, for nine-pin miniatures, though his inventory seems quite depleted, of late:    https://www.ebay.com/str/tubesandradio?_trkparms=folent%3Atubesandradio%7Cfolenttp%3A1&_trksid=p...

For Real NOS tubes Brent Jesse Audio , you can call and or email 
and he knows their sonics well and helps in matching  what sonic 
signature You are after ,30 day return for a exchange and you can buy 2 year warranty  based on the tubes cost ,NOS close matched 
tubes are getting scarce in some brands so not cheap, 
that being said in small tubes great buys are backup organ tubes 
much less Money for the exact same tube as the name brand 
with name printed labels like Hammond ,or other company vs  standard names  like Amperex , RCA, Sylvania,for-example.

Oh man Earl. I got a couple of guesses. :)

I have bought some tubes from various folks and I know you are looking for someone else other than Upscale but Kevin's always test great and last a long time. (I haven't bought any power tubes from him though.)

I have bought several tubes from various vendors, but found Brent Jesse to be the best. He takes his time listening to you (no interruptions) before recommending anything.

BTW, I've heard that the Qualiton XP200 sound really good with KT150s and 170s.