The connector has "TE" and "DYNA CLAMP" emobssed on it. TE would be TE Connectivity, so I went to their site and searched Dyna Clamp. Got some results, went to Digi-key and did some checking, and it looks like the connector you have is (drum roll)
A TE Connectivity AMP Connector, p/n 1-917807-2.
The link above will take you to the Digi-key page for the part that you have. If you scroll down the page a little you will see a section of "mating connectors," of which there appear to be four:
A panel mount plug, for installation in a piece of sheet stock, p/n 1-917809-2,
A through hole, right angle plug, for installation in a circuit board, p/n 1-1123309-2,
A through hole, right angle plug, for installation in a circuit board, p/n 1-1318983-6 (the connector here is rotated 90 degrees, so it lays "side down.")
And finally, the one you may be after:
A free-hanging (in-line) plug, p/n 1-917808-2.
I personally think Digi-key charges an arm and a leg for shipping, so be sure to order all the parts you need at once. Don't forget the connection tabs, which are the actual little metal blades that make up the connections - these are not generally sold with the connectors. There's a crimping tool that you should probably get if you're going to be making up a bunch of these connectors, but you could probably get by with pliers if you're only doing a couple. I'd definitely buy a lot more of the little blades than you think you'll need and practice before you do it for real.
There's also a removal tool that I'd suggest getting, again if you're planning on making up a lot of these. I don't think I've used these connectors specifically before, but I think you can generally release the TE connector pins if you have a pick or very small screwdriver.