Have a look at KWA magazines, KWC and KWA are pretty much interchangeable.
Are you sure you don't mean KSC and KWA who are two separate companies but practically have the same line up (except for KWA having the Vector)? KSC are Japanese based and do the R&D whilst KWA does the mass selling, both have their guns produced by the same factory but KSC have much better QA, an example of this is the KSC M93R which is a very good GBB Pistol (albeit plastic and with trades) but the KWA M93R is plagued with problems, both are exactly the same but as said the QA requirements are different for both.
Try these guys i found that they normally stock some rarer parts and are uk based:
http://www.milspecsolutions.co.uk/
Having done some brief research it appears that KWC is a el cheapo GBB pistol brand and TBH whilst i can find the pistol itself available for about £65 the mags are practically none existent.
Nonetheless i will refer you to the following HK company:
http://www.guns.com.hk/
I used them when i needed to get spare parts for a WE M92 Beretta CO2 Magazine parts, namely the magazine foot plate and BB feeder slide, as it was the CO2 mags and not the normal GBB mags the parts i was after were practically none existant out on the open market. Contacted them ordering 5 of each part for which the quoted me about £50 for all with a promised 2 months lead time. Lo and behold 2 months later the parts dropped though my letter box. I think they must have got the parts from the factory in wherever to send them the parts needed and then forwarded it on to me.
Ping them an email and see what they say, ideally state that you have photographs and part numbers would be handy, they normally reply within 48 hours in English, albeit from Cantonese Chinese via Google Translator.
