Perhaps you could transplant the good guts from one mouse into the other mouse's housing. In most mice, the sensor and logic is on one board, and the switches are on another, connected with pins or sometimes with a short cable, and in that case, you should be able to keep the switches and only make a new cable.
However, it may not be possible to make the logic board fit inside the housing you want. Perhaps there is a stem for a screw that is in the way.