There's a 1/8" aluminum heat sink disk in the top part under the LS with optics. The heat sink is soldered to the chrome/brass pipe using a little piece of the smaller diameter as a collar.
The circuit is max1797 on a SurfBoard adapter with conventional through hole peripheral parts to avoid etching a surface mount circuit board. It's mounted in the middle. The dimmer is a 10k potentiometer.
Two nimh batteries are in the lower section with some cotton balls so it doesn't rattle.
The lens is a piece of Plexiglas glued to a piece of the smaller diameter
PVC tubing. The battery end cap is made from the PVC pipe and a piece of
plastic electrical box. A draw string holds it in place.