Technically they're vambraces, with a bent more toward bazubands with the partial elbow coverage. I'd try a simple base of craft foam, then build up the cuff and elbow ridges with another layer of foam, dremel the details into it, and coat it in resin.
..or draw up a model of it, CNC it in layers, assemble the layers, smooth the sculpt, engrave details, and replicate the shape via silicon molding.