For the staff hmmm... Aluminum mop handle? Or a thick dowl rod spray painted silver? Yeah sitting with those side things is gonna be hard no mater what you do with it, and fabric stiffener wouldn't help alone... try a wire frame 16 or 14 gauge, (nice and thick) then chicken wire to get the curved part, you might want to cover the chicken wire with a single layer of duct tape or somehting to reinforce shape and make it smooth and less awkward. Then I would just glue the top with your fabric making sure to fold at least an inch unto the other side and then get a more exact pice of fabric for the bottom, unless you figured out somehow tro use gaffers tape or something paintable instead of duct tape for the bottum, I only hope they don't end up being too heavy!
Oh please tell me if I'm any help at all