Connector Recommendations

3.5mm panel-mount socket

Amphenol ACJS-NV35-3S

mouser.co.uk = £1.01 each

uk.farnell.com = £0.71 each

Datasheet to show dimensions

Other sockets should also fit, as long as the threaded bit will fit in a 6mm hole.
We recommend the 3-pole/TRS sockets as they allow the use of standard stereo mini-jack cables, but equally you could also use 2-pole/TS sockets, or 4-pole/TRRS depending upon your own requirements and instrument.

5-pin DIN socket, 180°, panel mount

Deltron 650-0500

uk.farnell.com = £3.57 each

mouser.co.uk = £5.05 each

Datasheet to show dimensions

The datasheet shows the thread to be 15.9mm, so any panel-mount DIN socket to fit in a 16mm hole should work. Remember these are for MIDI cables :)