Beware that TRS can produce all kinds of interesting shorts when you pull the plug under power.
Maybe one of those barrel connectors with central pin used in laptops or mini-DIN/mini-XLR, though the latter are probably too large.
Ahh yes I thought about that when deciding the pinout - in all cases it would effectively short the supply as well as cause a brief spike on the "enable" line (the third line). But this would be a semi permenant thing - I won't be plugging/unplugging very often and not when its powered. I'll probably be the only one using it, so I could have probably just gone with a permanent cable coming out the enclosure, but I like neatness. If this was for a commercial product, or for others to use, I would have had to add some kind of protection. I tihnk mini-DIN might be too large, given the plug is 9.5mm in diameter - the whole socket area is 9x10mm max.
Buy a small three pin "LEMO" from aliexpress. Almost the same space taken, 10 orders magnitude better that that stupid TRS.
That is the cheapest I've seen a Lemo, and I only require one ( the other end can be TRS as that has no size requirements) I didn't think they could go for <$35 US. The last time I used them I had to make up 60+ cables 5 way, hand soldering everything including the tiny sockets. Beautiful connectors, but the price was silly.
As I replied I realized, because I'm the only one using this, I could probably get away with 3.5mm. Cheap, cables are ubiquitous, and as I'm not going to be plugging/unplugging this regularly, I probably dont' have to worry about using the wrong socket. If I do, any damage would be my fault.
Cheers folks