Reb canteens didn't all have twigs and corn cobs as stoppers. The government actually made some. Surviving examples are super rare, but there are both dug and non dug originals out there, used on both Southern-made tin drum canteens as well as captured and refurbished U.S. canteens.
These are similar to their U.S. counterparts, just with a bit simpler hardware--two washers and a square nut rather than fancier caps and spanner nuts.
 
Make sure to include your mailing address with your order.  These will get shipped to you so you can swap out your stopper before the event.