edit: anyone else think it's silly that they sell only a seat post collar lock
but no lock for the saddle/top of the seatpost bolt? I dont know why they dont
do both.
They make this:
I'd imagine you could retro-fit the brake or dropout ones to work with a post like a thomson if you wanted to get really creative, you'd just have to find a way to have the solid end of the screw on the top of the clamp.
It seems easy enough, and I understand why they make the pitlock for it, but in what regions are people stealing bikes by taking the headset apart?