I don't know exactly what thread you are talking about, but really the "perfect bag for Disney" is whatever you are most comfortable with. Some prefer a backpack, some like fanny packs, some like a messenger style bag. As long as it isn't suitcase size Disney will allow it on the ride. You just have to be able to secure it. We travel with a school type backpack and don't have a problem taking it on rides.
That said, many DISers like bags made by Bagallini. You might want to lurk around the Tips board for more recommendations.
I hope someone else knows the specific one that you are looking for.