Sizes are currently most complete at Saks. But for additional colors or another set of sizes, try DvF, Amazon (additional colors here), Neiman Marcus, Nordstrom, Shopbop, Net-a-Porter, the Outnet (more colors here, here, here, and here), Lastcall, and Nordstrom Rack. A longer version can be found on sale here.
The style fits true to size for DvF. I am normally a 00P at J.Crew/Ann Taylor/most mass retailers, and the size 0 fits me okay (if somewhat baggy in the waist and sleeves). The dress in size 0 measures 13.25″ across the shoulders, 13″ in the waist, 15″ in the hips, 34″ in total length, and 16.5″ in sleeve length.
For more styling ideas, check out customer photos at Rent the Runway.