Folks asking for sources of parts sources should state where they are located.
The TV (cheap/free) HV section would likely require considerable effort and additional circuitry to reassemble a working circuit, which would likely then be iffy as far as reliability and safety issues, especially when utilizing used parts.
A new HV PSU, often contained in a compact metal enclosure, from a surplus supplier would be a much better option IMO.
Places like Fair Radio Lima OH may have new surplus HV modules/supplies made specifically for CRT equipment (not TVs) which may only require a common AC input voltage, and include a HV lead.
I bought one of these types from Fair Radio years ago, to replace a CRT HV supply in a large engine analyzer with a 10" CRT.
CRT HV supplies in TVs can be from ~1.5kV for small portables to over 30kV for large table models.
There are likely new surplus electrostatic HV supplies available from surplus suppliers.
There are probably numerous DIY plans online for HV supplies for all sorts of demonstration and experimental purposes.
HV supplies are also used in oil furnaces, and various other types of commercial/industrial equipment.