You could cast (and even patch-fit on a cyl bore) your own slug. Lee do a beauty which goes in a standard wad too. Factory sabots are also an option and have less leading than rifled slugs.
I agree that slugs are heavy for HD, ordinary cheap traploads are far better... unless you have a 25m hallway or stair with concrete wall backstop for the soft cast loads to mushroom onto when you miss !!