I am not going to claim to have the best pattern, but one idea that is very simple and requires no pattern would be to look up, or as me for diagrams, on how to make a \"long t tunic\" which is generally attributed to medieval re-enactment. Basically its a robe t-tunic that has a belled bottom so you can still move and the top can be as formed or as loose as you want. I have a few for my SCA persona and if you do it right you can still completely move in them.
If you want an exactly like the movie look alike you'd want to find a costume study site on jedi. If you just want simple monks robes those aren't hard to find. Beyond that I'd say if you make it up based on your own idea of a basic robe-based outfit that counts. Personally I would have to say that until the Order adopts a universal dress that has patterns and details on the site, a long t-tunic, a tabard, and a neatly folded sash would do nicely. As soon as I finish the stuff I am working on I will post photos.
