I'm not sure the Faraday cage will make any difference. Most of the better bike lights and flashlights are already inside one, in the form of their aluminum housings. Leakage paths for stray RF would likely be the switch, the battery compartment door, the charger port, if it has one, and of course, the lens/reflector assembly. And, that RF might be bouncing off the handlebar or something else. About all you can do is try moving the comp and light to different locations.

Do write to the manufacturers of both the comp and the light to inform them of the problem; they can at least look at design improvements for their next round of products.