I've been using this one fora little over a year on both my float tube as well as the yak and with 3 & 1/2 gallons its more than enough for the equipment as well!
http://www.overstock.com/Home-Garden...6/product.html
http://www.youtube.com/watch?v=vuBBM_h2BVA
It uses the same battery as the Ryobi 18v cordless tools as well.....