Replacing the whole blade with new copper contact, I've had no problems inserting small teet of contact into blade hole laying it on a work bench, the smacking the teet with a hammer. Mushrooms out fine and haven't had problems.

It's pretty soft metal so I'd think you could even squeeze the hell out of it with a good heavy duty pair of flat face needle nose pliers as well if just trying to put a new contact in the old blade still n the switch stack. Soldering is always an option that would work just as well.

Just make sure you can't spin the new contact by finger or needle nose pliers once your done as that could create intermittent connectivity issues