Soap ball-iron rich water
For me, I think of a plasma ball like a soap bubble floating around,. take a bubble making mechanism and use a gas.. to fill them, then let it float through a static charge area, its just a ball like water capacitor. I cant think of much you can do with it..but betting you can..
maybe just a conductive plate with holes in top lid.to make the bubbles,
at least the gas will ignite outside the cardboard tube.as the bubble brakes on the upper plate.