Researchers at the University of Sydney have made a small Polywell device which looks like this:
Notice there is no metal exterior on the magrid. As far as I understand… instead of using a magrid with a shell at positive potential (like the WB6 does), they are shooting in electrons with kinetic energy from an electron gun.
This seems like a feasible way to build a copper coil polywell. If the researchers are willing and able to share the details of the experiment, I would explore replicating the device and results. It looks manageable: