The extension is easy enough to find on the KelTec site:
http://www.keltecweapons.com/product/pf ... extension/(With an option for just the new baseplate, or a whole mag with it.)
There are certainly folks using armalaser sights on PF-9s
http://www.thektog.org/forum/showthread.php?t=244717You should probably join up over there also, since it's a lot larger audience specific to the gun.
(Err, also, that's the laser that's technically for the Springfield XD and is a lot less bulky than the one they have listed specifically for the PF-9.)
I don't like lasers on SD guns myself, but I really dislike the cheap look of the CT one and would probably go for the amalaser one if I ever changed my mind.