Proprietary connector seems unlikely due to the cost of underwriting a new electrical connection design (you will need cert one per country/region) for insurance purpose would scupper that idea. Also, you can buy the male (plug) end for a quid or two a pop from China, but I can't find the female (socket) end. Knowing the name of the connector should solve this problem in a moment.
Their pitch seems to be 4.5mm vs 4.2mm for Molex Mini-Fit Jr. (used by every other PSU OEM), but uses the same crimps. Guess I will have to try emailing Super Flower and Molex.