Will be used on a kayak and on an inflatable boat.

I had a hummingbird portable that had its own battery pack. Two 6V battery's in parallel to make 12V. Little suction cup for the transducer to the side of the canoe. It worked pretty good and it was around 100 bucks back then. If you have 12v available I would look for a used garmin combo unit like a 498.
Posted from my iPhone/Mobile device

Birds, sorry couldn't resist....

anyone have experience with the Garmin 150 Portable?