Hi, I just rebuilt my starter button on a CB 400F using the starter button assembly from an old Goldwing. I reused the guts from my switch and put them in the still intact plastic housing from the Goldwing. Suffice to say that I have the spring from the Goldwing start button if you really need it. It would need to be a pretty stiff pen spring to have any kind of longevity. The other spring I think that would work would be from spring loaded punch used for marking points in metal and wood work. You can buy them at Home Depot, It is the size of a pen with a steel point on the end and you push down on it and it "pops" leaving a mark in whatever material you are marking. I've had one apart and the spring is pretty stiff and probably just the right diameter. You could cut it to length with side cutters easily.