For factory matched new power tubes like KT120s and KT150s I've used reputable (100% ratings with thousands of transactions) Ebay dealers with great success (Upscale lists stuff on Ebay also), and have bought matched signal tubes from "thetubestore" (new and NOS) and Upscale (NOS). Most have been fine, although some Psvanes from Ebay were bad…oops...
