One can find Fanta Pineapple in the Philadelphia Coke territory (Southeastern PA, Northern DE, and southern NJ). I have only known it to be in 2 Liters, Fusion can probably verify other packaging.

Newport News, VA I have only seen it in 2 Liter bottles while Orange, Grape, and Strawberry are in 2 Liters and 12 packs.

And the easiest place of all to find Fanta Pineapple is Netgrocer.com. The shipping is actually not bad if you are on the east coast.

Netgrocer - Online Groceries and more, delivered straight to your door!

It is in the Beverages, Soda Pop, Other section

I bought 4 bottles of Fanta Pineapple from Netgrocer.com earlier this year, so they do legitimately sell Fanta Pineapple (although they were out of 1.5 liter bottles at the time, so they upgraded me to 2 liter bottles).