It is time to think how to hold everything together. I applied for the free student Fusion360 licence. I have to say the program is very nice to handle and to learn.

The idea is to hold the battery on the PCB with the three part threads. Just screw them together and it should light-up. The only compromise is the ground wire that goes from the PCB to the bottom part along the battery body.

I also made a join part to be able to have some versions with two AA battery stacked, making it taller and with a longer battery life.

Then I removed the dust of my M3D micro printer, far from the best printer nowadays, but the cheapest when it went out.