Under no condition can you use a VFD as a 3 phase source, they are designed to run motors only. There are solid state 3 phase converters that are designed as a 3 phase source. https://www.phasetechnologies.com/pr.../phase-perfect
A static converter is also designed to run a motor only, and can not be used as a 3 phase source.
The MultiCam will run fine on a rotary phase converter. As far as I can tell, a rotary phase converter does not generate any electrical noise. I have a customer that is running 2 MultiCam machines on a rotary phase converter. I have been running my CNC lathe on one for the last 4 years with no problems.
Also I have seen some MultiCam machines that can be connected as single or 3 phase. On one that I saw, there was a connection diagram in the cabinet showing both single and 3 phase connections. As far as I know, the only part of the MultiCam controls that requires 3 phase is the spindle VFD, the rest of the hardware is single phase, so you could just replace the VFD with a properly rated single phase input VFD and connect the machine as single phase.
Since you are missing the pendant anyway, why not just toss the MultiCam controls, and do controls upgrade? Most likely less cost than the pendant and would be a more flexible machine in the long run, and more compatible with modern CAD/CAM software, as well as having available support. Mach3, Mach4, Dynomotion, or Centroid Acorn would be good choices, all are compatible with your motors and drives.