Find an old 3.5“ Hard Disc Drive and open it with a Torx 8 screw driver.
Gently remove both plates with a lever. The first one will be easy and the second one is sometime attached with more screws from the back side of the HDD case. You also have to remove the read head with a screwdriver of the second one.
Put the two parts of thermal adhesive 1:1 on the plate with the stumps and mix the adhesive with a stick.
Place the LED on the adhesive and wait some hours until it got solid.
Increase the diameter of one hole on the flat iron plate with a metal drill until it fits to one nut of your board.
Attach an iron plate or another magnet to the battery with a thick heat shrink tube. Take a lighter and heat the tube carefully without burning the battery. Let the tube overlap on the side with the contacts for protection of the open contacts.
Solder the 9V Battery connector to the LED and fix the wires in one of the little holes on the magnet holder. Check if your plate is getting to hot with a fully charged battery.
Mount your optic with thermal adhesive or silicone and seal the open contacts. You can use the hull of an old bearing as a simple optic or an 3Mbumbon.
Connect your Beam Boarder to the board and start your night trip