I presently have an old Seattle Sports Hydrostar but for the life of me cannot figure how to change the batteries. I don't even remember what batteries it takes, yet it currently still functions.
Battery change instructions at
http://seattle1.nextmp.net/wp/wp-content/uploads/2015/03/Hydrostar-2013-WEB-4.12.13.pdfNot sure how important the red/green running lights are on a kayak since you move so slow relative to most boat traffic. I believe the legal requirement for paddle craft is a single white light.
The biggest priority is to be seen by other boats so you don't get run over. For that, a headlamp might be a better bet than a deck mounted light. Kayaks are so low to the water that being visible is a real issue even in daylight. A headlamp will be slightly higher than a deck mounted light. That extra foot or so of hight of a headlamp (relative to a deck light) will help you be seen more readily by power boats.
In my opinion strobes should generally be reserved for when you are in distress. One exception might be if you see a powerboat bearing down on you in the dark and suspect they don't see you. In that case I wouldn't hesitate to tun on the strobe to keep from being run over.