Make your master out of your armature wire, clay, and whatever else you want...then make a mold using a urethane resin, or silicone mold rubber, and then use platinum cure (Dragonskin) silicone to cast the brace. Pigment the silicone so you don't have to paint it. Make sure you sculpt an overlap so you can 'glue' the bracer together with more silicone. Voila!