Macbook Air 13" - 8GB RAM in retail locations?

Hey guys!

I've been mulling over what laptop to get for a few months now. My current Macbook (mid-2009) is at the end of its run.

I was torn between the Macbook Pro and the Macbook Air (13" on both counts), but then settled for MBA for several reasons. I work with statistical software such as SPSS, Stata and SAS on a daily basis. The extra resolution on the Air is a huge bonus for me - viewing more data at a glance makes a world of difference. Moreover, the advantages of running an SSD is tremendous. The MBP has SSD options but they're ridiculously overpriced.

The issue at hand is the following: I need my laptop to have at least 8GB of RAM. I will be running Windows software via Parallels or VMware almost constantly. I'm in the Dominican Republic so I can't buy off Apple's online store (they don't accept Dominican credit cards - trust me I've tried). Amazon doesn't stock any 8GB builds, which would've been a solution.

My parents will be traveling to New York and Cape Cod next week. Do Apple Stores (the official retail locations) keep upgraded models or is the 8GB option strictly build-to-order?

Many thanks in advance for your help guys! If I can't buy an upgraded Air, I'll have to go for a Macbook Pro (which I can upgrade myself with 16GB of high-speed RAM for about US$100).