You could do something as simple as using vinyl/pleather/leather and using craft foam or something for the gold elements. It's not a real sword so you don't have to worry about a blade slicing through the scabbard (and leather is a traditional scabbard material, anyway).
Just trace the sword, add seam allowance and sew the two pieces together. Will be a pain to "turn" but relatively easy and straightforward. Make sure to clip seams at curves and it will be fine (the decorations cover the end, anyway). You could even use something like buckram or two layers to make it thicker but it just depends - vinyl is pretty thick on its own.
Just giving you a radically different alternative.