The Harley locking caribener works well. If someone wants the helmet they would have to cut off the D-ring which would make the helmet useless.
Useless? After an accident a decade ago, during which I slid for a few feet on my face shield, the paramedics cut the straps to remove my helmet. I was still on my back when they arrived because after I had turned over there was a guy standing over me that said "I'm an off duty cop, don't move". The guy at an accessory shop, where I buy tires, told me he could replace the straps.
It was a seemingly minor incident, except for the totaled out scooter and the check an attorney gave me, but I replaced the face bar scratched helmet anyway. I guess the LEO and paramedics were just being cautious because I wasn't injured and was riding another scooter as soon as I got home from the E.R.
Slip a pair of handcuffs in my pistol pocket. If Im stopped anywhere and away from the bike for awhile, Ill grab em. One end wrapped around throttle and recess in frt brk lever with a closed front brake (bonus points for frt brake locked) and other end locked thru d rings.