I was wondering about those, too (of course, I'm a 10, so ... well.) I much prefer the single knot myself, in fact I have a Donald Pliner slide with a single knot and a similar heel (slightly higher), in black, and they were a great purchase--dressy but very comfy, great to wear at a wedding.
There are a few similar options on Shoes.com, but they cost about double (still a great sale). The plus side? Available in just about all sizes. Here's the link:
Donald J Pliner Women's Hare Shoe - Free Shipping