KWA parts are the same for the most part (just some plastic/metal slide differences) and most of the KWA catalogue is stocked by ASG. Therefore: email an ASG stockist and you'll get most KSC parts. What is it you need?
Not sure if its what youre after but i got a few KSC/KWA parts from here got my glock... http://www.univairsoft.com/en/144-original-parts-ksc-kwa Not sure if they got the parts youre after though
They get about all of my pistol-related orders now. Price and part availability for the Marui stuff is basically unbeaten by anywhere else.
Therefore: email an ASG stockist and you'll get most KSC parts.
What is it you need?