I think that is what you are looking for. I don't know of any stores that carry them, I've only seen them online. Your best bet would be to go to a search engine and type in "shotgun speedloaders" that should bring up several online stores.
Personally, I've never used one, and I doubt I would recommend them for Home defense. It's one more thing to break, and I doubt you can perform a tactical reload (load with the shotgun on your shoulder, ready to fire) with them.
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