You might want to check out this Ninja 650 Air Horn Install DIY, you'll probably find it useful. I've installed both the Hella Supertones and the Nautilus Air Horn, and yeah, aftermarket horns can be a real pain to install due to size.
What do you mean by "on the OEM socket"? Do you mean the mounting point, or electrically? I mounted mine to the engine mount bracket which was the only place where it was physically possible to put it, pretty much (see the link above for pics). If you mean electrically, definitely use the OEM horn pigtail to send power to a relay. The OEM wiring is NOT sufficient for an aftermarket horn. The OEM horn takes about 3 Amps, whereas an aftermarket air horn is closer to 23 Amps. It will sound on the OEM wiring, but you are liable to either blow the fuse, burn the wiring or just get less sound out of it if you do.
In any case, good luck with the project. To be honest, it's a pretty big PITA to install, but of all my mods, it's possibly my favorite.
Be careful using the stock wiring. The new horn may pull more current and blow fuses. Most folks use a relay in place of the horn and wire the new horn to the battery, through the relay, with an in-line fuse.
The mini was designed for stock wiring from my understanding. It seems like most people just use it stock. My friend's Ninja 250 and and 300s have no problems with the stock wiring with it either. The full size one definitely needs more power though.
The Lidlox is made out of some type of hard plastic. The one I ordered uses a bolt from the front brake lever. Then their is just a small key that unlocks it. I don't think it's super strong, but in areas that aren't really bad I'm sure I could leave my helmet attached for a bit (after taking...
I know Europe got the helmet lock that can use the ignition key for a single key. It's 2019 and I still don't see it listed for 2017, 2018, or 2019... How has this not been addressed yet?
... but anyways is there anywhere in the US we can order these yet?