Got one!

[dtvmcdonald]

You could do what I did while my CT-100 lacked a working 15GP22.

I bought a pro (but not broadcast) grade Sony monitor of appropriate size and
devised a small convertor circuit board which used six transistors to
convert the CRT grid signals to 75 ohms, and hooked that to the monitor.
It ran off a wall-wart secreted inside the TV.

I didn't put the monitor in the cabinet, but it would fit, barely. It had a gorgeous picture. The convertor had lower capacitance than the 15GP22. It demonstrated just how good I-Q is with a bright picture.