I use Cateye LD-600 as it happened to be on-sale at LBS when I was getting set up to Bike-The-Strike a couple years ago. I then discovered the Cateye online small parts store which has clamps for every conceivable size of frame and seat post that you would ever want, which was great as I could now move the light from one bike to another without reinstalling. Got some rechargeable AA and haven't yet had a problem.