Some of these have a little spot for a tab to fit into. Might have to get creative on this one. I've even used super glue, behind the locking nut to keep on from spinning.... Not that I recommend it!
Hi Disassembling the Lock Cylinder is difficult. There is a steel pin driven into a blind hole that retains it. The pin can be extracted with difficulty, after which it could be replaced either with a new pin or the hole tapped for a setscrew.