Tube vendors.

Vintage Tube Services, If your looking for something REAL NOS from a guy that has speakers that are rated at 115db sensitivity who listens closely to every tube for sound quality, from someone who has been buying testing and selling tubes forever, who owns some of the oldest and original tube test equipment as well. If you have the time to wait then get in touch with ANDY and tell him what your looking for. The vintage RCA 5ar4, and 5687's for my Tube powered Modwright SWL 9.0  are very special and make this pre amp a giant killer.

Matt M

@mattmiller thank you for the insight.

Appreciate all the input and I do not appreciate one who PM me, he was a bit of a dick. 
You know who you are.

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...