VINmounts Tough Claw Large Locking Clamp Base with 1 " /25mm/B size Ball for 30-63mm Rail VIN-B-031-lock
Replace the regular knob on the VIN-C-031 with the VIN-LOCK-C lock core knob, including brass 1/4 "-20 threads, so you can loosen the tightening of the knob.
Once you have your mount set up where you need it, you can lock its location and feel safe in case it gets lost, and the device you mount will stay in the right place.