You can also take a quilted potholder and fold it in half and stitch along the side and bottom. Works perfectly.
I had some padded material and just made my own design and sewed one up, and then turn it right side out and put bias tape on the opening..this may help
Sew4Home had a free pattern recently. It may still be available.
I think Sue in Engineered in Stitch may have on for sale. Her designs are great.
I don't know of any free ones, but I know Embroidery Library has one. Also there is one at Five Star fonts. Love Chris