Summary

I have seen many similar designs but none was a perfect match for what I wanted:

• Housing attached to left hand side of printer - to connect the camera cable with the nearby camera
• Have the camera cable penetrating the housing
• Have connectors in front - for connecting the printer AND plugging in a USB stick to load models/gcode
• Additional power cable hole for the LEDs to illuminate the bed
• Use a rather small fan (30 x 8 mm, 5V)
• Have the buck-converter inside the housing
• Be able to attach the housing using only T-slot nuts (and two M4 screws)
• Minimize needed parts (some design used an extra part to attach the housing to the printer)

To attach the housing to the printer (I attached it to the left / lower T-nut frame), you need 2 T-slot nuts and two M4 screw (I guess I used M4x10mm)

To close the houring, I used 4 self tapping, counter sunk M2.3x8 mm screws
To attach the raspi and the buck-converter to the base, I used 6 self tapping, counter sunk M2.3x6 mm screws

Before closing the housing, attach the M4 screw and the T-slot nuts.
After closing the housing, you can use a hex wrench and the two holes to teighten the screws and firmly attach the housing to the side of the printer