I had a busy Thursday and Friday, so My favorite Sutler is coming to you today!
If you're looking for a great price on an authentic shelter half, then Heywood Shelters might be just the ticket. I'm not sure of their status, but they might be worth contacting. According to the site, their product was reviewed well in the Watchdog, and is a reenactor-made item.
They make both the 1862 and 1864 model shelter halves, although the late model seems to be the default. They also offer the shelter half in two cloth weights 10 and 8oz, both of which seem to be authentic choices.