Alto II keyset connector plug identification

Would anyone be able to identify the 19 pin connector used on the Alto II keyset? Shown in the second photo on https://www.computerhistory.org/collections/catalog/X124.82C The Xerox engineering doc (209962B_Alto_II_Assembly_Keyset.pdf) has it as P/N DE51218-1 if I interpret it correctly. I've looked for a while and the closest I can find appears to be Mouser p/n 2DEF19P The cost of 136 USD (each!) is more than I (and perhaps everyone else) would really like to pay, and that's only for the male end. Ideally I would like a datasheet on this original connector if possible, to know the pin-pin spacing and the pressed metal surround dimensions. I've just ordered small trial quantities of screws, microswitches, e-clips, nutserts, rods and so on for my keyset lookalikes/workalikes. Also about to start the key mapping to F5-F9 using a popular small SOC board, which is small enough to be inside a custom printed shell that the keyset plugs into. That is, the 3-row 19-pin female connector side which goes through to USB. I was thinking there's no reason it shouldn't be able to work using the original connector with a real keyset-less Alto, should any such animal be lurking out there. Hence looking at the feasibility of placing in a 19 pin male-female connector arrangement rather than the fallback of straight-through to USB. The whole thing is still at prototype stage so even if it doesn't work out, well I will at least have a bunch of additions to my nuts/bolts/fasteners/switches stash. Thanks for any help, Steve.