This was one of my very first farkles when I picked up my FJR. As the owner of an '86 FJ1200 that has a built in helmet lock, I was a bit surprised to find the FJR didn't come with any. I came up with this really low tech, low budget helmet holder and it has been working great for me since '04.
Start with a package of computer wire straps (hook and loop type) - available at your favorite office supply store:
I prefer the straps with the slot on one end to feed the other end through, as you will see in the shot below.
Wrap it around the frame rail under the seat. Feed the tab end through the slot end.
Now when you need to hang your helmet, unlock the seat, slide the 'D'ring through the tab end of the strap and fasten the strap to itself. When you put the seat back on, the strap will not be visible to passersby if done correctly. The shear strength of the velcro is more than enough to keep the helmet secure, especially with the seat back in place. The only way a theif can make off with your lid is to cut your helmet strap, and no helmet lock is going to prevent that sort of theft.
Anyway, I love simple, low cost solutions, and this works for me. Good luck! :lol: