Evidently these are 6Pin ATX connectors. Found some on eBay and be here in a few days. The L3++ running fine on 3 boards once I disabled the Reboot on low hash rate.
OC
No, odds are they the ubiquitous PCIe connectors. There is no such thing as an 'ATX' connector.
That said, odds are ones from ebay or other grey-market sites are crap. As long as you do not unplug/plug them more that a couple time they should be fine but will wear out after just a few mating cycles. It is far better to get power components from reputable distributors such as DigiKey, Allied, Mouser, etc. where you can choose the type and quality you want.