I bought a shoe stretcher many years ago from Kleenezee. Great buy - I lend it out often as well as using myself. Think there might be a way with damp newspaper but other will know better.
Put a freezer-bag in the shoe with the open end upwards and fill it with cold water then seal it with a plastic tie and put it in the freezer...inside a plastic grocery-bag if you want to separate it from any food. As water turns to ice, it expands and so stretches the shoe. Leave it there overnight then remove and let the water melt. Job done in my experience.