After years of looking for info on how to replace this spring I've figured out a way.  
To be clear,  there may be an easier way and I'd be happy for someone to post it.

I machined a punch to brace the large head end of the new extractor pin and a second punch with a .098 hole and turned to size to fit inside the recessed area on the other side of the bolt.  This allows the second pin to push the spring over the head of the pin and clip into place.. Lined it all up with the hollow punch in the drill press chuck and pressed it on.

I'll add a pic later this evening.  With the punches I made for reference.

Hope this is helpful.  I'm sure FN has a tool for this but I'm not aware of one in the wild.
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