Where can I get a dress pattern like this (pic included)?

Look at the full skirted, thin straps sundress in the pattern books of Simplicity, McCall, etc.. You can find some of them on line. Now depending on the double ruffle figure out what the material you want for it will be and it should be coordinated with the pattern of the dress. You can make it by measuring around your body or the pattern. Some people would divide the measurement by 1/4, 1/2, or 3/4 in length depending on how full you want them to be and the width would be of your choosing. Email me if you need further information.