I think you should consider some balsa sheeted, foam floats. They can't leak and they can't sink as others can. I am very pleased with the 2 sets I have.

Before that, I used Prentis floats from a cutter in Niagara Falls, Canada, but he closed up.

[link=http://www.geocities.com/planefunfloats/]Plane Fun Floats[/link] has pre-sheeted foam floats of all sizes. They are in Michigan, which is up your way.