Smaller magnets, Hall effect sensors, 3D printed parts that take 10 minutes to produce, there’s nothing insurmountable here. I have been collecting reed switches in different sizes for a while now. I suppose one could print 4 lobe cams for microswitches too.
Do you have a 3D printer? I can post the .stl and you can give it a try as I’m not sure when I will get to. This part was just to do the initial printer setup and prove out the cad to real part pipeline.