I am entirely unable to understand how you can say "a pump does both of those jobs pretty neatly" without actually having at your disposal anything remotely resembling a theory that does any sort of job of matching observation in which charged particles are pumps.

I just meant that a pump can act as a source - or a sink - depending on which way around you use it.

A specific model would probably not help much. My position is that there are a whole class of models which are isomorphic to conventional physics and exhibit T symmetry. We don't yet know which of those models are correct, or indeed if any of them are.

The Wheeler–Feynman Time-Symmetric theory appears to be one such idea.