Wearing a poncho over a climate-controlled metal carapace that covers your entire body sounds a bit absurd, though admittedly very stylish. If backpacks are out for "realism" reasons, what about messenger packs, duffel bags, strapped guns and other things you sling over a shoulder? I think fanny packs and other belt items sound like fair game, too. If the oversized pauldrons prevent you from touching your hands together behind your back, you could lay it flat on a table or something and pick its ends up.