What about the simple, 89 cent Bic lighters? I've left them in my pocket during a wash cycle, took them out afterwards and they work just fine. I don't know if that constitutes as "waterproof" but being in a washing machine for 25 minutes had to give it a good soaking.
I have also swam with a Bic in my pocket. After about 15 minutes of drying, it worked like a charm. I think I'm going to do a test tomorrow, just to see what happens. I'll put a Bic in two feet of water for about an hour, then see if it lights up. And, of course, I'll post the results here afterwards.
John McIntire