Alternative to the bed cleats to secure a bike lock

I have a 2008 Tundra with the rails on the sides of the bed. The Toyota cleats are fine for tie downs but I can't fit a heavy duty bike lock cable through the tight opening. I ride often and keep my bike inside the covered bed for days at a time, so I would like to find a way to secure it to the side rail rather than just rely on locking the gate and the lift door on the bed cover.

Any ideas?