Chair Help

[Rich Torino]

Recently I made a couple of Adirondack chairs for Wifey. Nothing fancy, basic design made from southern cypress. She's happy with them....except......now she would like to be able to "roll" them around the patio. My thought was to use a type of spring loaded caster on the rear leg that would raise it slightly off the ground when there is no weight in the chair. That way she would just have to lift on the arms and "roll" it wherever. Does anyone know of a source for this type of caster if they even exist?? And I am open for any "better Ideas".

Thanks
Rich in Florida