Solid question. Since the jacks are plastic (aside from a small ground pin in the hole) it's pretty easy to "tap" them with an M3 screw so that's what I have on my build, but if you can find something approximately M3 diameter with coarser threads you may have an easier time getting it in there.
All the parts I need to build up the revised Supersonic boards should be here tomorrow (should have been yesterday, but customs decided to hold onto the package), and I will also have parts to do a more formal Nobelium build doc.
Mouser shouldn't be the only place to source the jack, that was just the first place I found. Amplifiedparts used to carry them, but they showed up in clearance a couple months ago and disappeared shortly after. The part number I list on the BOM is the Amphenol part number, there's a comparable Neutrik part that's the exact same dimensions and is a drop-in replacement, I just need to track down the part number. I've used Amphenol XLR jacks exclusively for a while so I don't know much about the Neutrik.