Here is where I bought my hard case for my Mortimer 54 cal flintlock.
http://dixonmuzzleloading.com/index.php?section=muzzleloadingshop&link=contact
I always deal with Chuck Dixon. He should be able to put you on the trail to what you're looking for.

I have purchase a gun sock for all my m/l here is a guy that makes them @ I have to say they work great,his prices are not bad $20.00 that includes the shipping.They are not hard cases but they do prevent any damage to the rifle ,which I like his e mail is below
cottonwood@networksplus.net

Russell,

I don't think they list one but the people at Track of the Wolf will surely know who manufactures such a case. E-mail or call, they are very helpful and positive.