Skipping the issue of why, as well as pros/cons of doing so, is it possible to add an external safety to to a P320? Parts available? Walk through of procedure?
I've called Sig several times regarding this topic and have been told each time "not yet". They say it may be available in the future. I haven't asked lately though. Time to call again.
Sounds like a good excuse to buy another gun
Problem is FCU is different.
And FCU is the serialized part.
Seems it would be far easier, safer and cheaper in the long run to sell your non-safety gun and buy one that came from the manufacturer that way.