Generally speaking the answer is no. The exception would be if the company you are portraying was a militia unit prior to the war and a breast plate was part of their uniform. They may have kept it for a while. The CS quartermaster had enough problems supplying the necessary accouterments without including a useless item such as a breast plate. You can take a look at some original items here: http://www.angelfire.com/ma4/j_mayo/csequip.html