Keep your eye out for the new Oxyride battery developed by Panasonic corporation. They are due out in April. They are a new battery technology which is suppossed to last twice as long as regular batteries today at about 10% increase in cost. I think they are coming out in AA and AAA. They are developed for digitial camera usage, but may benifit fish finder and head lamps.
http://biz.yahoo.com/ap/041210/japan_battery_2.html