This dress is fairly simple, a halter top, waist band, cut out below the waist strap at the back, sarong-style long skirt with a dipped hem.
It's easy to lengthen a skirt and dip the rear hem, and to add a cut out, so don't worry about those features. It may require a little planning and testing, but mixing patterns, one for the bodice & waistband, and a different one for the skirt, is do-able.
So look for a pattern with a halter top and waist band. Ideally it will have a sarong-style skirt of any length, but if not, look for a second pattern for the skirt only.
Ignore the pretty photos and color illustrations. Look at the black and white line drawings, and read the descriptions, looking for halter top, waist band, sarong or wrap skirt.
My favorite pattern site is www.sewingpatterns. com
They carry thousands of patterns from nearly 100 different pattern companies. Click on "dresses" and you will get over 3500 results. I am sure that buried in there somewhere are one or two patterns that you can easily modify
For fabric, I'd use one of the gorgeous print poly charmuses at http://www.fabricmartfabrics.com/xcart/Charmeuse-Polyester/