355 Smaller windshield mirror

I find the 355 windshield mirror's size and location obstructs forward vision. Especially in tight right hand corners. You know, where the bicyclists are.
I want to mount a smaller mirror on the existing windshield post and have found several that might work. However, I don't see an obvious way to remove the existing mirror case from the ball end of the post. Is this a 'press fit' that can be pulled apart? Or does the case have to be unfastened from the inside? If so, how is the the glass separated from the case to allow inside access? The hard plastic retaining strip/band that secures the glass to the case has been impervious to any attempts at removal. Hasn't budged. Will hot water expand it? Any suggestions how I can open the case? Is there a way?