There is also an OEM buell option PN N1027.1AK helmet lock with keys. You will have to drill and tap to mount it. I have one still in the box that I've yet to mount, planning on top left side of swing arm behind oil reservoir. I bought it from ASB back in the day but the keys don't match my bike. Maybe ordering from Harley they can match the key though.

https://shop.newcastlehd.com/part/n10271ak