Somebody posted a picture of something like that, which you can buy. It was on
Island_Sand's Float thread. Its like an inner tube with a cover than opens on the top (providing a shaded storage area).:
I think somebody posted a link for a site which sells them in the USA but I'm unable to find it now. It might have been a tyre/tire cover but I have a feeling they sold the whole thing.
Still, making your own might be cheaper (not always the case). That stretchy, tough, shiney waterproof material they make Dutch fisherman's waterproofs (excellent for glissading) & triathlon wheel covers from might be ideal.
