That looks like the right switch. The newer mice used a smaller switch like this one... the old mice used a switch that was about twice the size with a shorter plunger. We did a fair number of these repairs back at the store in the day... The one thing to watch for is the height of the button. You might have to sand off a little of the lever on the bottom of mouse button itself... (not the switch) Or you might need to superglue a little plastic to the microswitch button to raise it up.
