soundy- if you can't find anything else, you can use thin cardboard (like cereal boxes) and papier mache, then spray-paint. there are more sophisticated methods and fancy products that people buy specifically for armour-making, but if you are on a budget... you can make a basic papier mache by watering out glue or by mixing flour and water. cut out the basic shapes in cardboard, add the ridges and details by taping on balled or rolled-up newspaper scraps, then papier mache over. you might also want a glue gun to stick the pieces together. The one thing you'll want to watch out for is the paper curling while it's wet, but this is a very budget-friendly way of making things, since you can recyle a lot of what you need instead of buying all the supplies.
