Gavin, I would not even know where to start to determine the type of metal that the terminals are made from to know what process to search for. They look like brass, but that covers a lot of ground. And as I mentioned before, 2 of the terminals have been hot in the past and they are just plain weak. Not much to work with. I believe they are past the point of no return and need replaced.

Natcho, I don't know if the switch will take the heat of soldering wires onto the posts. The posts are very short and are bedded in a phenolic like plastic. If the switch would take the heat, then something like that would work. But if it didn't, these switches are a pain to find and expensive. Frankly, I would be afraid to try to solder on them.