Well...

You can take a regular CRT and rewind the deflection coils on the yoke to work as a vector CRT display. Arcade Jason has a good video on how to do this.

https://www.youtube.com/watch?v=Ci9qiGVMF7s

Then you need a vector generator if you don't have an OG vector game. This one on Github is pretty good and can be connected to either an oscilloscope or vector monitor.

https://github.com/english1234/vstcm

If you use the vstcm to drive your rewound crt, you still have a problem. The deflection coils are very low impedance (around an ohm I think), so you need an amplifier stable at very low impedances that can generate a voltage sufficient to get deflection across the full screen in x and y. I think Arcade Jason was working on one of these too but I don't think it is out yet. ElectronAsh was working on one as well but I don't think he finished it.

https://www.youtube.com/watch?v=tybGveLtlkA

https://github.com/ElectronAsh/Vector-XY-Deflection-Board

Or you could follow iz8dwf's amazing series on how he built a black and white vector monitor.

https://www.youtube.com/playlist?list=PLbKEoUHtoVucsrySlogDz...