You have two other identical posts. Please delete them by clicking on the "Delete" button at the bottom of each post. This will help clear up the clutter on the boards.
As for your question, I doubt that you'll be able to get any armor for less than $100. The materials alone cost more than $100, not counting the time and effort needed to put them together. You should try pepakura. It's not as bad as you might think. I personally prefer this method to cardboard.