Pecatonica River Longrifles can supply just what your looking for.
http://www.longrifles-pr.com/
Although their catalog shows the stocks semi-finished with the lock mortise cut, they will also supply the stock without the mortise if you choose to use a lock that is different from the one they usually use. (The lock they show in each stock style in the catalog.)
That would allow you to install any flintlock you have.
All they need to know is the barrel channel size, the kind and grade of wood you want and the style of the stock (like J Dickert Lancaster, Lehigh, etc.).
You will have to buy a lock and they can supply you with one of those too.
Give Dick Greensides (the owner) a call at 815-968-1995. Tell him what you want and I'm sure he can make you happy.
While going thru the catalog in the above link remember, you will be looking for the style, the kind of wood and the grade of the wood if you want to use curly maple.
You will have a LOT of work to do to finish your gun as although the stocks are nicely sanded, they all require a LOT of wood to be removed from all of the surfaces to look like they should.