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The issues with reproducing vintage CRTs (or other vacuum tubes) are multiple, and interdependent.
Most of the people who actually designed and built these things are at very least long since retired, if they are still walking the earth at all.
A LOT of the process documentation (the "secret sauce" if you will) was landfilled when the production lines shut down decades ago. The RCA Vacuum Tube Design books are a good overview, but not complete. Many detailed formulas for phosphors, cathode coatings, etc. were the highly prized "IP" of the day, and were never made public.
Most of the process machinery met the same fate as the documentation--landfilled or cut up for scrap metal.
When manufacturers stopped building tubes, the specialized supply chain that fed the factories shut down immediately afterward. The exotic metal alloys, ultrahigh purity chemicals, specialized tooling, etc. that were needed to make QUALITY tubes suddenly had no market and just disappeared from availability.
Many of these problems could be overcome with money, of course. But unless you are able to guarantee a consistent, ongoing demand for tubes, it will be difficult to get manufacturers (even in China) to gear up to go into production of the needed materials OR the finished products. Even the audio tubes that are still in production don't ship enough units to justify the supply chain commitment needed to truly reproduce the vintage stuff. And the musical instrument and high-end audio tube market FAR outstrips the potential market for reproduction 7JP4s...
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