Not trying to steer you one way or another. I would just hate to see you invest in a rifle and find out that it is not something that is widely accepted for re-enactments.
Something like this might be nice:
http://www.dixiegunworks.com/product_info.php?cPath=22_92_186_191&products_ id=891&osCsid=eabd2feff3dccd18e791daee3c27fd0a
Or:
http://www.navyarms.com/html/products.html
Perhaps a kit can be found that is NSSA approved for a little less?
Good Luck!
Tahquamenon