Bacpacjac, the BSA Hotspark works pretty well. You can order it online here:

http://www.scoutstuff.org/BSASupply/Item...3&item=1167

Although I am a cubscout den leader I have no other affiliations, just a happy customer. This is the one I have on my necklace at the moment. It's also what pushed me to add the pill fob (with watertight seal) with some reliable dry tinder material that can take a spark. As my skills at finding tinder in the wild improve I may eventually eliminate this but for now it is going with me.

On a sidenote, the striker is already becoming a bit discolored just from the contact with my skin (sweat, oils, etc). As I am sure it is just a piece of carbon steel, this should be taken into consideration when using in a water environment. It may be a good idea to consider either a second watertight pill fob to hold the steel and striker, or just one to hold the steel, striker and tinder.