Anyone know a source for obtaining a 'locking knob' (has a lock cylinder built into it) for a RAM motorcycle mount. The set-up I'm using has 1" diameter balls and the arm is 3" long. The knob I'm referring to, is the plastic 'wing nut' that holds the two halves of the arm together. I've found the 'locking knob' for 1-1/2" diameter balls but none for 1" diameter. Any help, advice, input would be appreciated.