I use a princeton tec rage for a neck light after trying many. Totally waterproof, BEYOND bright, and is 11$ at west marine. I can bring mine to a meeting if you want to check it out in person. Only drawback is the "twist-on"... wish it was push button.
The LED penlight available from thesurfcaster is what I have been using. Nice and small, waterproof, and has push button on/off. Not super bright but plenty bright to get around. Posted from my iPhone/Mobile device
Threaded Mode