There's a locally owned sunglasses store (can't remember the name) just outside security in JAX that carries Serengetis.

I just received my pair from flightsunglasses.com. I haven't flown with them yet but so far I'm really happy with the quality and the gradient of the lense. Great experience at flightsunglasses.com, I called the owner and he kindly answered my questions and had my pair shipped out really quickly. Best deal I could find on the Internet for that pair and free shipping as well