The originals had a cardboard piece about 2" wide along the edge of the pocket, sides and bottom, this was to cover the steel rivets used to hold the side clips on, Those brass notebook paper bend over things from Staples work for this.
The vinyl went over the top metal edge and inside the pocket.
I have used 1/4" foam in place of the cardboard for a more defined look around the edges, but cereal box cardboard was what the original was. Just enough to cover the rivets.
The vinyl folded over the edges of the side clips.