Let me expand on this a bit. I am disappointed to report that our initial testing was mostly a flop. Probably too much bypass between sections and the filter wasn't a high enough MIRV rating. But some information revealed, so we're marching onward.
Regarding electrostatic filtering, it's still something we're considering, with some added knowledge.
Honeywell "Electronic Air Cleaner" cells, aka electrostatic cells, are available used on ebay relatively cheaply. These consist of wires and charged plates, so there's nothing to wear out.
The power supplies are a different story. The power supplies are built into racks that the cartridges plug into. They supply something like 8KV and 6KV with connections to alternate plates. This should be within the range of neon sign transformers, and the max current is around 10mA as I recall.
I have not found any reference to anybody using a neon transformer in an application like this. An HV diode or bridge, perhaps a filter cap and some HV-rated resistors to make a suitable voltage divider. Sure seems like it should work. Arcing to generate ozone probably is not desired here, so the current draw would be insignificant.
Of course, everything would be interlocked, bleeder resistor across the filter cap, air flow switch to operate only when the blower is running.
Comments? Suggestions?