What I used to use years ago, and what I am "having made" right now, was/is a large burlap bag (4' x 4' x 2' approx. ) filled with scraps of sheet foam from the shipping dept. at my brother's job. Basically the same as some of the bags on the market now just bigger and cheaper. (both the burlap and foam were free, I just have to sew it into a bag, fill it and sew it closed)