You will first have to make certain there is space for a spring. If the gun was made without them the pin is likely bottoming on it's shoulder & if you add a spring in there it will not fire then. What sort of protrusion are you geting now without them. Is there a second shoulder that will allow a spring to be fitted, some just don't have provisions for one. Mike's source is a good one as long as is space to fit it.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra