The filling happens to be feed corn. My local feed and seed store carries a fifty pound bag that has been screened and sifted several times for extra cleanliness. For eight dollars or so I can fill a lot of bags.
It's super simple to make :: just a plain insert that is segmented into five sections and a pretty little slipcover that can easily be removed for laundering. I tested it out on my grandmother and she loved it. We decided to make it a couple of inches longer on each end next time, but that was just our preference. This could be made in all different shapes and sizes to fit little people too. It can even go in the freezer to be used for bumps and bruises.