Per the FAB-Defense website, ALL of their products are made in Israel.
Here are some collapsible sights that would work with your gun.
https://www.opticsplanet.com/magpul-mbus-rear-flip-up-back-up-sight-gen-2.html
The FAB Defense Tactical Single-Point Bungee Sling should work with the FX9.
The FAB Defense Tactical Single-Point Bungee Sling attaches using a QD sling swivel mount, and I don't believe the Keltec KS7 has one.
The FAB Defense Tactical Single-Point Bungee Sling will attach to a QD Sling swivel, so if you have a QD sling swivel on your shotgun it will attach.
Yes, if you attach it to a QD sling swivel like this: 1S0-SV-SLS
The PC Charger has QD attachment points, if you do not have a QD sling swivel, you will need one to attach the sling to: 1S0-SV-SLS
You would clip it to a sling attachment point
Yes, you would just need to attach it to the sling attachment point.
You could clip it to the sling attachment point on the side of the shotgun, or attach it to a QD swivel: 1S0-SV-SLS