Some guys favor a bigass Bowie just for style points but I think they get in the way. I prefer this one a fella in Maine made for me out of an old saw blade. It's got a 6 1\2" blade and comes in handy for cutting patches, leather and for removing the occasional stuck cartridge case.
here are several vendors that handle knives like Dixie Gun Works
https://www.dixiegunworks.com/index/...s+%26+Sheaths/
and Track of the Wolf
https://www.trackofthewolf.com/Search.aspx?search=knife
And go here for fun.
http://sassvets.homestead.com/index.html