I'm looking for a fishfinder I can use out of a canoe.  The transducer has to be able to be removed easily, it needs good battery life, and the battery pack needs to be a reasonable weight.  It'll be used on local lakes but also up in the Boundary Waters for week long trips, hence the battery requirements.  

 

Any suggestions?

Every depth finder can easily be used on a canoe. None come with a battery or a transducer arm, you have to get those separately. There are several clamp on transducer arms available or with a little ingenuity, you can fabricate your own. A small 8ah battery is available to power it. Check with a store like Batteries +. If you shut off the unit when you don't really need it, the battery should last a week. They always did for me on my fly in trips. I used to use a small tackle box to transport the unit and battery. I drilled holes in the top to mount the depth finder bracket and carried screws with wing nuts to hold it on the box.