Have your Napoleons always had trouble staying in place? edit
I just checked and mine say "Napoleon - Made in Japan" on the inside of the the stem.
Mine are Napoleons like yours, but I had to modify the rubber mount to get then to fit inside my bars, so I probably messed them up (less rubber bung to expand) . There are Chinese copies that are sold at Cycle Gears that use a metal fitting that looks to me like it would be far more secure.