expanding a SHOEBOX to accommodate five lines

[wsher]

I'm wanting to jerry-rig an extra edge connector to integrate a fifth line to an existing four-card-slot shoebox (with this 5th card to be physically outside, but wired into, the KSU/panel box).
(Such that a 6-button phone set can access 5 lines)
 
A  KTU (400) line card edge connector width is just under 3" and i'm wondering if anyone has a suggestion for a currently common off-the-shelf female socket.
The KTU contact pitch appears to be about 7 contacts per inch --> ~ 3.63mm   (an odd pitch for current times)
whereas today's common generic sockets are typically 2.54mm pitch.
I was hoping to find something that is compatible.
(rather than trying to scavenge/cannibalize an old KSU box.)

Does anyone have suggestions/experience?

[reference an old topic: https://www.classicrotaryphones.com/forum/index.php?topic=9241.0    but there's no mention of a source]
i have a (double sided) edge connector 
EDAC 305-036-520-202 (from mouser) with 3.96mm pitch   and it sorta matches the KTU 400D pins but is off by 1/2 contact width across the span of the contacts.   It would be unreliable even if i got the pins to just align once...

[wsher]

image showing Comparison of 400D card edge connector vs. conventional (modern) socket
THe clearest view is using the connection side of the socket, which of course has the same pitch.

[payphone2830]

I wonder about a good source too without cannibalize an old KSU..

You may want to look at this ITT 584C panel on Ebay. You can cut the wires and remove the card connectors. You can also leave the connector connected and just make the wiring changes as the back panel can be removed. Plus you get 14 card connectors and extra fuses. Not bad for the price....

https://www.ebay.com/itm/294529631383?

The other thing that I can think of is to just take a old 25 pair cable and solder it to directly to the card if you do not care about the card.