Do they make a fish finder that works on normal batteries? I use a kayak so I don't have a motor / battery.

they all work on batteries but you will have to get a specific one for the fish finder you have depending on what type of finder you get.  I use a 12v 12 amp hour battery myself and i can get two trips per full charge.  And i am in a kayak as well

Alright thanks

I use a motorcycle/atv battery. Bought the battery at Napa auto parts. It fits nicely in an old plastic tool box which sits in a milk crate on rear cargo area. As an added bonus this set up becomes my ice fishing sonar later in the year. Can fish for many hours on a charge.

I think the Fishig Buddy is portable. 

The Humminbird Fishing Buddy 130, for example, uses 6 AA batteries. Check out their complete lineup. Some even have side finding capabilities.