Since my friend needed several equal figures, I made resin copies of the prototype. The following photo shows how I encapsulated it in plasticine, made a frame with stiff cardboard and created a two part mold with room temperature vulcanizing silicone rubber.
Vaseline was used to create a barrier between the layers. I find that it works better than liquid vaseline and brand demolding sprays, besides being much cheaper.
Here is a quick video showing the demolding of the prototype, once the rubber was fully cured:
An this is how it will be used. It is a paper model that can be found at Papercube and that is reminiscent of M.C. Escher's stairs: