Fanta is a flagship product of Coca-Cola (now with over 60 flavors) does numerous test markets all over the U.S. and the World. The results of those tests, determines if there is a market for a particular taste. In San Diego for example, Fanta’s market is the strawberry, grapefruit and orange. In some parts of LA, you find more of a variety adding grape and pineapple to the list. And in some remote areas of Colorado and Montana no one has heard of Fanta.
Until your town or city demands the flavor ( Kolita) I would not expect it to be at the local stores soon, due to the high cost of marketing it or ROI (Return on Investment).
As for the kolita syrup, I seriously doubt you will be able to buy it in the US for personal use since I have never seen it in soda dispensers unlike others (orange, strawberry) where a business gets it from Coca-Cola
You can order Fanta Colita from numerous Costa Rica online stores at a reasonable price. Below is a couple of links to some of the online stores:
http://www.ticotimes.com/costa-rica-products/
Here you can buy it:
http://ticoshopping.com/index.php?main_page=index&cPath=49_64
I hope this helps ....