Surplus Sales of NE has some NOS 12" electrostatic deflection & focus dual beam CRTs for $125.
Dual beam here means two complete independent electron guns and sets of deflection plates.
This tube isn't for everyone.. modern design with aluminized screen wants 7500V not 3000V.
I'm thinking of large modulation scope application. There's always a catch. This 1958-design tube has a P19 phosphor usually used for radar. It's an orange, moderate to long persistence phosphor.
While a long persistence is inconvenient sometimes, a moderate intensity level, plus a peak-detecting brightness gate could enhance the intensity of the trace when peaks occur so the important waveforms are highlighted.
It's all good fun with dual-gun! Just thought I'd point out this large tube at an unusually reasonable price for those willing to accept its weirdnesses.
page -scroll way down to 12ACP19:
https://www.surplussales.com/Tubes-Sock-Acc/CRTtubes.htmlgood data sheet:
https://frank.pocnet.net/sheets/201/1/12ACP2.pdf