The PCB itself is 4 x 4 inches, and fitted in a custom Bend-And-Fold box (aka BAFbox). 

This is slightly larger than will fit in the off-the-shelf extruded cases for 100 mm Eurocards.

I suggest that the new board be resized to 100mm square, to allow the use of such cases. And also that the audio connectors are moved to so they stick through the endplate, instead of the side which is harder to drill through.

See https://www.farnell.com/datasheets/1933057.pdf

Not cheap at £30 each but cheaper than the time spent trying to find or make alternatives. If you fit a silicon disk in the same box, 

IDC sockets are £5.80 each from Farnell. Two needed per kit, or 3 if you allowed for Silicon disk on same cable.

60-way boxed headers are £2.67 from Farnell.

A right-angle header with ejector lugs is £1.33 from Farnell.