I have found a book that details the sharpshooter from both sides. It is "Sharpshooters of the American Civil War 1861-65". Author is Philip Katcher and published by Osprey.
I beleive the badge you have run across was a eight-sided black cloth with a scarlet felt cross worn by Henry A. Wise Co. B, 2nd Maryland Infantry. According to the book, badges were not branch-wide,but designed by each branch for the purpose of identity on the feild. Some of the badges were a simple red cross on their arms and others were a red band around the left elbow with a red star above it. Barry Benson of South Carolina recalls using small pine twigs stuck in the hat bands to help keep his group together.
There is a lot of information in this book.
2nd Regiment Co.D