perigalacticon:
Is anyone aware of a kind of 'quick disconnect" pin that would be able to enter a standard PCB hole and expand to make contact with it? Something like a miniature banana plug.
You mean something like this?......
Although, the male part doesn't appear to be the banana plug in that diagram.
The issue with producing miniature banana male plug is maybe due to not being able to get enough spring strength .... due to the relatively small dimensions and not being able to get enough spring force.
Also, a pcb hole has limited hole depth. It's not like a regular banana plug hole, which has adequate depth to get some nice function etc for the male plug to wedge itself into there.