You need CAD software, a CNC milling machine (you can rent time on it), a lot of spare time and even more persistence.
I don’t like plastic. Instead, I like nature and that’s why I have developed and now produce wooden mice. They are beautiful, pleasant to hold in your hand and make your hand less sweaty.
I managed to obtain a decent result only after five years of work in my spare time. For already more than 4 years I have been using mice of my own production. During this time, I had to develop new electronic stuff twice to keep up with the times and not lag behind progress.
Everything started with handicrafts. In these models, I used stuff from conventional mice.
These experiments resulted in the understanding of the impossibility of making a normally working mouse using manual technologies. It also became obvious that I would have to develop my own electronics to suit my housing without trying to adapt it to the borrowed stuff. The maximum that one can produce with handicraft technologies is a single capricious specimen that will be worse than a conventional plastic mouse. This did not satisfy me and I got down to serious work.