Larger diameter mic in smaller holder.
 

To capture stereo I would like to attach a spare Sony ECM-MS2 I have to my JVC HM150. But the Sony is 24mm in diamater and the cylindrical clamp mount on the JVC is more suited for 19-21mm.

What options do I have or what would you guys recommend?

Attach some extender to the screw and use the original clamp mount?
Get something like the Rode SM5?

Re: Larger diameter mic in smaller holder.
 

The OEM mount is probably not worth the trouble and cost of modifying. I would recommend the 'Rycote InVision Video - Shoe Foot 42901' which also isolates the mic from handling and camera/lens motor vibrations.
I'm sure you're aware a camera mounted mic is not good for picking up dialog, no matter what mount.. or mic.

Re: Larger diameter mic in smaller holder.
 

Thanks Rick, I'll look into that one.

Yeah I know camaremounts are not optimum for dialog. I will use the Sony for location/ambient sound.
For other situations I use an AT3031 / AT835b on a rycote pistol grip.