I noticed on twitter that one of these was being demonstrated.
Here is one I built. I got the aluminium tape from Aldi and the bowl form Asda. I painted a table tennis ball with aquadag (Timstar or any science supplier). There are conducting spray paints out there.
I have attached a pdf with instructions, I did get this off the web but cannot find it again to give credit to originator. Van de Graaf works well just don’t forget to earth. This one has a pith ball in it from an old electrostatic demonstration kit It is easier to see the connections in this clip
I’ve found an attachment talking about a mass spectrometer, it didn’t help me understand the wiring. Why is it sparking on one side of the bole and not the other? On my list of projects is an electrostatic motor using aluminium tape and plastic drinks bottles, but in that case the electrodes are far apart so you don’t get any arcing.