You really nailed the shape, it looks dead on. I wouldn't suggest molding it though. All the lines from the tape will show up in the mold, and if your going to be buying expensive casting materials you will want to make your prop as detailed ans as smooth as possible. What I suggest you do is get some bondo spread it onto the surface carve the details in, sand it like mad, and then you'll get a nice finished product that will look good molded.
For molding you have several options, the cheapest is to get some 100% silicone caulking and acrylic paint. Coat you finished prop in cooking spray or a very thin well spread coat of Vaseline, then take your caulking, and with hands wet in soapy water spread a thin layer over the props surface. Make sure that there are no bubbles on the inside. Once this layer has cured mix more caulking with a bit of acrylic paint (this makes it harden faster) and add a thicker layer. Once this has cured make a wavy cut around the contour with a sharp knife.
For a better but more expensive mold you can get various casting silicones from stores online. These are NOT cheap.
Once you have made your mold, you can our either casting resin or fiberglass resin into the mold to take a cast.
Hope this helps.