Afternoon Adam Helmer
I have one of those you are referring to, It laces on the butt of the stock (you can't use your patch box) and it ties round the barrel, (can't sea the sight and can't put your ram rod back with out a hassle) so I got one of these commin in brass
under Accessories,,
Miscellaneous Accessories,,
\\\ Sling Swivel Hardware (bottom of page)
http://tcarms.com/
Now, my friend,, If any body want's to make one, This is what I found this mornin and made mine,,
http://www.saroftreve.com/wwl/braiding/3trick.shtml