It’s not really possible to ground a good insulator like PVC (or acrylic etc. etc.) as they don’t conduct.
There are various anti static sprays and coatings that can be applied to give insulating materials a thin coating which is sufficiently conductive to drain away the static charge. This is unlikely to work on the workpiece being cut however.
It’s also worth noting, unless it’s lightning, in which case you need rather different precautions. Static electricity has very little current and only needs a tiny leakage to ground to bleed away the charge. You don’t need thick wires or low impedance connections to ground, most anti-static items are only partially conductive and it’s common for them to have a high-resistance connection to ground for safety reasons.
Those who’ve had success wrapping a non-conductive hose in bare copper wire have provided a discharge path for charge buildup on the outside of the hose to ground, before the hose can accumulate sufficient charge to zap the frame or stepper wiring. The hose is not grounded, but the static is being discharged before it can upset the machine.