My first thought was to find out how much a replacement bladder to go inside a football would cost, but that idea went out the window very quickly once I tried a couple of sports stores and discovered that not only is it impossible to buy a bladder, but all of the modern balls are one-piece plastic things with no replaceable bladder.
And so it was that I went to a hardware store to buy a bag of salt, and to a few op shops looking for a doll about the size of a newborn, some sort of waterproof bag, and some sort of fabric bag.
I ended up finding a child's beach ball at an op shop for the waterproof bag ~ I can cut it open, fill it then tape it shut. After looking at cushion covers for the fabric bag, I ended up finding a stuffed toy hippo (merchandising from the movie Madagascar), the body of which is about the right size and shape for the fabric bag, but it would need the padding, head, arms, legs and tail removed and sewing back up. I didn't buy it at the time, but went back the next day and got it.
At another shop, I found a doll. I was originally intending to get a hollow plastic doll, but had realised that the hollow ones have rigid arms and legs and a body that would not curve into the foetal position. When I found a soft-bodied doll about the right size, at first I wasn't going to get it. I walked out of the store, then changed my mind and went back in and bought it.
In the next instalment, you'll get to see my mutilation of the doll. :P