How many positions has the connector have?
2. This one is 24 signal and 12 power
http://www.digikey.com/product-detail/en/3-6450860-5/A108375-ND/4022487
img
Number 2 looks like it might work. Below is a picture of the back of the supply. The PSU looks to have 20 signal. I doubt they would line up appropriately or the spacing might be too wide. Awesome site though. I did find this through browsing and looks like it might be a match. Need to look at P7 though on the datasheet. Looks weird. Unfortunately, no stock a min order qty is 264 @ $6.18/ea. Not a bad price if it is the correct connector and there are enough orders. Might be able to request a sample or a smaller amount?
Let's continue searching... (looks like J4bberwok had already replied)
Part Link: http://www.digikey.com/product-detail/en/51939-045LF/51939-045LF-ND/1491654
Drawing/Datasheet: http://portal.fciconnect.com/Comergent//fci/drawing/51939-045.pdf
Could you turn that PSU over and see if there are any markings on that connector? If so, could you try and read them then transcribe it here?
@J4bberwok - I can not find that part number anywhere, not even on the FCI site, so looks like it must have been a custom one. It does look like a powerblade connector nevertheless, and though I have seen a 6P 24S 6P, I can not find a 20S one, but short of it being custom, I am sure one can be found ... just a matter of looking for the right MOQ's.