Nice thing with AA batteries is you can buy a set from Harbor Freight tools cheap and they will probably last 2 trips before a recharge. And those units that use 2 6volt batteries work well but they are bulky and batteries are expensive. ( I used one myself but now it is wired it to a lawn/garden battery.$18)I noticed that it appears that the Fishin Buddy line of products has been taken over by Humminbird. (Not positive on this, but they are using the same name and look very similar, so I assume some kind of takeover occurred):
Humminbird 110 Fishin' Buddy Ultimate Portable Fishfinder
I looked at the Fishin Buddy products, but decided I didn't want to deal with AA batteries.....