My Big Sister cosplay.
I used paper mache and foam to make the helmet, with red LED lights inside. Most everything else is made with foam, Worbla, PVC pipe, and other things.
The tank is made of a rolled up posterboard and foam. It is hollow with a detachable top. There are 2 straps running from the front side of the corset under the chest piece, attach with clips, which helps keep the chest piece pulled forward while keeping pressure off my neck.