Vett asked how I rig it up in another thread. Heres what works well for me.
Waterproof container that holds a 12v lead acid 7 amp hour battery. Add a cigarette adapter for whatever you need, spot light, submersible light for night fishing, aerator, phone, etc. I used velcro to hold the battery in place. Now I can set it wherever I need. Rubber feet on bottom so doesnt slip.
I have three ways I mount it. For the kayak, i used PVC trim board and PVC to make a flip up mount that uses existing handle holes. I used to use velcro through the scupper but figured I'd get interference like that since moving to side scan sonar. I also have a flat board I mount to for when using a Jon boat. Just hold it on with c clamps at the top. Basically just like how your motor mounts to your transom. Takes me less than 2 minutes to rig up. Seems to work well for me.