Material/Compound for Mold

Do you only need 1-off? You could make a plaster of Paris mould of the sole & take it to your nearest investment caster. They could make a wax copy from the plaster mould & cast it in the metal of your choice.

If you have anyone close with 3D printers they may be able to laser scan the sole & print a 3D plastic copy.

There are a number of urethane casting compounds available. They come in liquid form. You will need to coat the sole with a release agent and use one of the harder compounds. Make a box out of wood or metal, fix the sole at the top of the box, and fill it with the liquid urethane. It will harden over night. Then remove the sole. This will leave a rigid mold that will fit the sole.

thanks Guest & Nigh, 'googleing' :'urethane casting compounds' put me on a right track