Cookieman:
Good question! I've got an elastic carrier on the 45/70 Handi, works fine, very convenient, wouldn't do without now. Leather would really be nice.
Come to think of it I've never seen what you want either, and I'd like one too.
Cabelas has leather cheek pads, but not with the shell carriers, 25 bucks.
They also have leather cartridge carriers that fit on your belt, 12 bucks. Other than buy em both and sew em together, or visit Tandys and do it yourself, I don't know. If I knew where to go, I'd get...3.
Woodbutcher