If the rod & tube are both metal, tinning a layer of solder on the rod would work, but is labour intensive. A slight bend in the rod might be enough to do it, or a few strikes with a chisel on an anvil. I suspect the factory might chose the latter as a quick fix.
Mole grips might persuade the tube into a less than round shape, but protect the visor with a neoprene shield at the very least.
If the rod is soft metal, molegrips might just squeeze it out of round enough to grip.


DaveW
'05 Red Roadster S1
'16 Yellow (Not the only) Narrow AR GDI Plus 4