Class 1 is readily available (that is what I use, made by Katmandu which is an outdoor adventure chain like Eddie Bauer). The study you cite concludes that it is effective: "Stockings were effective and are an easily applied prophylactic measure, especially given the difficulties in trying to exercise in modern aircraft" so I'm puzzled why you start by saying it is not effective and then cite a study that contradicts that!

My personal experience is that I feel better when flying with compression than without, even for F flat-bed travel and lots of exercise on-board. But I sometimes spend 40 hours a week on a plane, which becomes a factor.