Can you find red brass pipe? That would be the best way although I am not sure if you can find a metal J box. I suppose they still have them but I have never seen anything but PVC

I think that brass "conduit" is really plumbing pipe anyway (tapered threads) because it needs to be water tight. If the AHJ is on board I would use a brass coupler and an RNC male adapter. Your bond wire is just taking the equipotential grid to the J box. That grid allows any chapter 3 method of splicing. There should also be a EGC in the lamp cord.

Greg Fretwell