Nowadays, please your old C64... give him a modern joystick with at least second fire, C64 GS style
I'd really love to see this option more, although I don't have such a joystick.
OT: But isn't this a forum with highly creative members?
Maybe someone finds an easy way to enhance existing joysticks with a second button? For example I could imagine that you could re-wire a button of a Competition Pro joystick, but probably you would have to change the cable.