Zappos but you can find them on Shopbop and Neiman Marcus too.
Here's a recent outfit that I wore with them that I posted to instagram.
In my search I did find a couple more that I loved, I really wanted the Loeffler Randal Mara but I couldn't find my size. I liked that the Jeffrey Campell ones came in leather and love the lace ones from Tory Burch. The ASOS espadrilles are really cute and a great price! Ultimately I settled with the Rebecca Minkoff ones as I liked the ratio of the espadrille part (not too big) and the detail of the studs and the comfort. But I love the look of these so much I may be buying one of these other options too.