Yes it'll fit, I picked up a Glock 17 Serpa 2 years ago for a KSC Glock 18C.
Oh ya if anyone else cares, the Glock 17 Serpa fits KSC Glock 17 (duh) and KSC Glock 19s too. It doesn't work with TM's Glock 17 because the slide is slightly thicker, if you replace it with a metal slide though then you'll be ok.