First, kudos for Jojo cosplay. I'll be looking forward to seeing it at con.
For the chains, have you checked any Halloween stores? There's the Halloween Warehouse in Beaverton (open all year), and they should have overly sized chains on something that you could just spray paint. if not, you could always attempt to make them out of sculpty or something but I'm sure the results would be much less pretty.
For the belts, it should be simple enough to do. It looks like it's made out of fabric so you could just have your friend (or even do it yourself if you can sew a straight line) sew two pieces of fabric together with some interfacing. Paint one of the other colors of triangles and you have your belts. The buckle for the belt might be a little difficult to find but start Goodwilling/Buffalo Exhanging/Joanns/Amazon to see what you can get. If all else fails, you could use high gauge snaps to keep the belts on your pants and make a buckle out of foam, but you'd want to paper mache that sucker a million times and paint over it with resin to make sure you don't accidentally squish it when bending over.
Hope that is some helpful information though. Good luck!
