I still use a Wizard mouse. I've had it since '95 and it still works as well as the day I got it after every day use. Brilliant piece of hardware. But I'm looking at it now and it doesn't seem to have any way to open it. I don't see any screw holes. Maybe the screw heads are under the teflon pads, but I wouldn't bet on it.
I tried to get another one as a potential replacement some years ago. Apparently Wizard Developments changed their name to Compute!, so that's a clue if you want to go looking for a replacement, but they seem to have gone. :-(