I think you will find the trigger is not the problem, the safety parts do not contact the trigger. The trigger is just a lever acting on the sear, the sear is what would have to be modified to change the sear engagement or the engaging surface cocking block, or both - check that surface to. It also might be a worn safety push rod that is allowing the sear to move to far when the safety is on. If the sear feel firm with a reasonable amount of pull with a crisp release and it doesn't discharge when hit hard with your hand it might be just a worn or bent safety push rod.
Numrich has sears but is out of safety push rods.
ADDED - I tracked down an older thread that has a little information that might be helpful -
topics/13492264 After reviewing this it looks like the safety push rod moves back at an angle so it should push the sear into full engagement as it's set and hold it there, The arm is quite long and has a weak point where it's slotted in the middle, it looks like it might get bent just by pulling the trigger to hard with it engaged.