Welcome to the site. Always good to see some new blood.
What you need are Musket Caps. They are a bit larger than what you are going to find for pistols and run of the mill other BP long arms. You will have to get them from a place that supplies them, which usually means ordering them from some place like Dixie Gun Works, although they aren't the only supplier. They usually come in cans of 250 and generally last a pretty good while as bp shooting is a lot slower process and most of us don't deplete our possibles as quickly as we do with smokeless powder guns.
Here is a link to one possible source and one possible brand.....although it is a good one, RWS the brand.
http://www.dixiegunworks.com/product_in ... ts_id=3723
Old muskets are pretty simple in the parts structure. I got an old Nepal copy of an 1853 Enfield that was pretty far gone working, more or less, not long ago. There is a post string some place. Most parts for these old guns can be found today because of the Civil War reenacting craze.
Is your rifle an "original" or a reproduction?
