Hi Kurt,
I am very interested in seeing any photos, or learning who can make one. I don't think the Buntline case photographed in "Peacemaker" and the case seen in Sellers book on the sharps are the exact same though. The Sellers book photo shows a Sharps case made for the Sharps company, specifically for the Creedmore matches, meant to be carried by hand with a handle for the purpose.
The case made for Ned Buntlines Sharps (pg 289) was for an 1874 (Serial # 160009 .45 2 7/8 cal, 30" barrel, and double set triggers), and while similar lacks the handle for carry, and seems to lack the pocket for the long range sight case, but has a strap and buckle on the side, hinting it possibly is intended to rig to a saddle like a more conventional rifle scabbard.
They are definitley related beasties, though, and made possibly in the same year, probably by the same company contracted for the creedmore match case. (the Buntline rifle and case invoiced to E.Z.C. Judson, Stamford New York, May 7th 1877).