I'd advise:
Putting tape on the slide (to protect it) before removing the OEM front sight.
Place a piece of paper/tape or non-marring tool over the sight before tapping it in place.
Place the sight down on a solid, non-marring surface (not a table mat) to do the flaring.
Use a hammer.
Yes, currently XS is only selling the Big Dot sight with posts for "C" series Kahr pistols as an in-house install.
You can buy their Big Dot sight for other model Kahr pistols (these have a front dovetail) and have a local gunsmith do the install, but the local smith will need to mill a front dovetail on your CM9's slide.
Regards,
Greg