All the paper I used was from Paper Source as I could pick it up in town. (See, again, lazy.) I cut the paper exactly the length of the binder; I did not wrap the paper around the top and bottom. I covered the spine and about two inches of the front and back cover. I was concerned (as was a commenter) about how the opening and closing of the binder would affect the paper, but it does not seem to be an issue. The paper does not gap or pull away.
The acrylic magazine holders are available at CB2.
I am looking for labels for the binders so that I can signify, well, something. I'm not quite sure how the tear sheets will be filed. By subject, as they currently are? By designer? By magazine? Oh, gentle reader, these are the things that keep me awake at night.