^Hmmm, well one way to make the belt is to just use cotton fabric with interfacing inside or any other fabric that has the correct stiffness and paint/applique the triangles on. Or just find a real belt and do the same thing.
The wig does look alright. It's recognizable as Rin although to make it better, I would say trim it a bit shorter. Do you have a friend that has some knowledge of cutting wigs? It's actually pretty simple to do if you feel up to doing it yourself.