If you wish to get crafty, you can probably put together some kind of EM shield using aluminum foil or another metal. It should connect electrically to some part of the bike (as a ground - I know, it's not a ground, it will probably function well enough, assuming you aren't running carbon). if you have a particular light and computer arrangement you like that will stay fixed, you could probably make a shield that was fairly small, but you'd have to play around a bit to see where it needs to be. I do not recommend simply wrapping the light in foil. While probably effective electrically, it may cause heat problems with the light.