Scooters have ignitions you need to put keys into.
there are no keys on a motorized scooter.
I have been making my own keylock covers for CDI's for years.
They were a standard feature for my first ~25 builds but just an option now.
I re-wire the whole ignition from Mag to CDI standard, and that requires some kind of CDI cover anyway, done just right there is room for a alternate kill switch.
The trick is finding a small keylock switch you can put in a box you can attach to your CDI.
REALLY old PC cases had them, that was what gave me the idea back in 2009.
I have been using 2 different ones I can actually buy.
The big one on the left was the best as far as the key goes but big and way expensive even buying 50.
The little ones work but have a dainty key that is hard to use but really cheap and if you pay attention to when using does the job.
I just wire up the mag and throttle kill button and superglue the wires to the CDI side.
Solder on the keylocks wires then EPOXY the keylock cover to the top of the CDI.
It won't prevent anyone from physically stealing your bike, but it will prevent them from ever starting it until they buy a new CDI because if you epoxy it right, busting the cover off takes the CDI wires out with it ;-}
All nice and fine if you know your way around electronics and a soldering iron, but just not an option if you don't.
It's a time consuming pain in the butt to do right and not something you can just 'add-on' to stock wiring, an ignition keylock is just a side benefit of complete re-wiring.