Let’s startup Kicad, do the schematics and play a bit with the PCB drawing. I have in mind a design for a 3D printed case, we’ll see that later.

Several times now I ordered PCB from OSHPark, and never been disappointed. I could use their manufacturing precision to down size the board area up to 17x17mm, giving $2.45 for 3. I let an option for a push button, we never know…