I purchased a picnic cooler with wheels, but realized later that it did not fit in the caravan. Therefore, I had to find an alternative. Since I could not find any smaller ones that have wheels, I purchased a convertible hand truck. The hand truck can be converted to a trolley that will allow one to use it as a picnic cooler transport device.
An alternative that should be considered. Putting a smaller, non-wheeled cooler on a convertible hand truck tied down with bungee cords is a great way to transport a smaller cooler that is too heavy to carry.
A convertible hand truck can be seen also at Home Depot at http://www.homedepot.ca/webapp/wcs/stores/servlet/CatalogSearchResultView?storeId=10051&catalogId=10051&langId=-15&N=0&Ntk=level1&Ntt=hand%20trolley&Nty=1&D=hand%20trolley&Ntx=mode+matchallpartial&Dx=mode+matchallpartial&s=true