You won't find commercial patterns that you can use as-is for this costume (unless there is something new I'm unaware of out there...). I made the shirt and outer tunic for someone a few years ago and had to totally redraft patterns to customize them.
Granted, I made this for a female so the shirt pattern block I started with was a woman's. You could just as easily start with a men's dress shirt pattern and draft a mandarin collar and the bib construction.
Base Pattern Used: McCall's 4381
collar used: Butterick 3345
Fabric: Cotton Twill subtituted for Wool Gabardine. Gray Kona cotton used for bib lining (this might be lighter in color than the original, but it's the best we could find).
I studied quite a few screen caps and photos of Luke, and I felt that the best way to have the bib hang open like the real costume was to design the layers of the bib more like Han Solo's shirt. It doesn't zip up underneath or button up. I only added 2 snaps inside to help keep it from shifting, but they may not even be needed.
Here the lower flap of the bib is pulled out to give you a clearer idea of my design:
Pattern Block Used: McCall's 8155
and collar from Butterick 4401
Modifications Made: My final pattern doesn't look like the McCall's pattern at all. This was only a rough starting point so I'd have something to drape with. The shape of the front opening is different, The arm cycles are deep V, the waist was tapered inward, a seam was added in the back at the waist to help with shaping and eliminate baggy bulk. Facings and lining were added as well.
Fabric Used: I suspect the real costume is made of a heavy, slubby silk (it has the look of heavy linen). Neither was in budget for this project, so a heavy linen was used. (A weight for jackets or upholstery). The fabric was distressed with sanding blocks (Thanks to The Pariah for that suggestion), then washed several times in very hot water to fade the color (I even threw in a tennis shoe to try to get it distressed a little more).
Since the linen was still a little thin on its own, I added Kona cotton lining to add more body to the vest. I don't think the real costume is lined though (I think I can make out where the arm hole facing tacks on to the outer fabric in screen caps.) If I had to do it over I'd probably line with black muslin, as the kona cotton is a little stiffer than I'd prefer.
You may also noticed I added a seam to the scarf bit in the center back. Although I don't see evidence of this on the movie version, for the size and shape I was making this costume it was the only way to have the grain of the fabric line up properly in front on both sides of the tabards.