Firstly, it's not actually a low pressure switch. It's on the liquid (high pressure) line of the A/C system and it is in fact a high-pressure switch. It breaks the electrical circuit to the compressor if the liquid line pressure is too high. There is no "low pressure" protection in these early Z factory systems.
Secondly, I know you'd love to just put in a stock replacement that won't require any modification - after all, then it's just "un-bolt one and bolt another one in" - but you're not likely to find a stock replacement. I've been that route...
You're probably going to need to find a replacement that will still be available years from now and re-do at least part of the liquid line routing to fit the new one. There are multiple products available that you could substitute that also have provisions (ports) for your threaded pressure switch.
The liquid lines are made from standard refrigeration tubing and use standard flare fittings. Coming from a plumbing and HVAC background, this is pretty simple stuff for me. I can understand that it can be daunting for some though. Still, any refrigeration shop worth their salt (or HVAC tech as a side job) should be able to handle the liquid line modification. Completely new copper refrigeration tubing can be easily formed and flared to fit the new part... And possibly re-forming (bending) the existing tubing could be all that's required.
1974 "Early" 260Z: '83 L28ET - F31 ECU MAF Coil TPS - T04E - FMIC - 400cc Injectors - MTX-L wideband - NIStune enabled! - '83 5 speed - coilovers - Big Brakes up front - Sakura Garage, Tempe, AZ