Comment by Animats

Hobbyist-level production of monochrome TV tubes is possible, but a big effort. Some of the early television restorers have tried.[1] Color, though, is far more complicated. A monochrome CRT just has a phosphor coating inside the glass. A color tube has photo-etched patterns of dots aligned with a metal shadow mask.

CRT rebuilding, where the neck is cut off, a new electron gun installed, and the tube re-sealed and evacuated, used to be part of the TV repair industry. That can be done in a small-scale workshop.

There's a commercial business which still restores CRTs.[2] Most of their work is restoring CRTs for old military avionics systems. But there are a few Sony and Panasonic models for which they have parts and can do restoration.

[1] http://earlytelevision.org/crt_project.html

[2] https://www.thomaselectronics.com