We have two sets of Wildwasser Large overnighter airbag/drybags for rent in our shop. They are also for sale, but it may be a good rental for someone who wants to try them out or doesn't do a lot of overnighters. They rent for $2 for the first day. Here is the link: http://www.whitewatertube.com/Wildwa...TAL_p_344.html
For those that don't know what these are, they are a drybag with an inflation tube so they can be used as flotation in the stern of your boat. I find them to be indispensable, especially for overnighters.