I have a system from an SI. It came with an EVGA 1000 GT. I don't have all the cables. I need an extra 6-pin cable to power one of the Corsair iCue link AIO and fan sets. Is there a way I can just order a compatible cable set for it? 
Thanks in advance for any help. 

You could try contacting support see if they have any you could buy. Another option is to buy one from a site that makes custom PSU cables.
 
https://store.cablemod.com/configurator/  one of many sites that make custom PSU cables. Shop around to find best deal.

Please contact EVGA at Support@EVGA.com with the registered serial number of your PSU for assistance.