I just got the STM Bags Alley Air Small for 11" and 13" MacBook Air from eBags. Got the bag today, and wow, it actually exceeds my expectations.Great looking bag! Let us know how it is when it arrives.
I picked up this guy for myself.
http://goincase.com/products/detail/nylon-sling-sleeve-cl60034
It fits the 13" MacBook Air like a glove.
Here are some pics with the 13" MBA to show the size, fit, etc.
It's literally a perfect fit, with an dual interior pocket that protects the MBA from surrounding space, etc.