fancy dress tin of sardines

i would like to dress up as a tin of sardines and cant find a fancy dress costume anywhere.....it has to be uber laght weight as its for a festival and i dont want to have to carry it about....also waterproof.....and cheap......CAN YOU HELP ME!!!!

Try cardboard boxes, look for something with rounded corners, IKEA would be a good source, then paint a layer of gloss on the cardboard. Add your design, seems lazy but it'll be light resilient and fairly waterproof...