I use stevia in my coffee and oatmeal much of the time, and used to enjoy the former Starbucks Mocha Valencia, which was discontinued a few years ago, as well as Cafe Vienna instant coffee drink (another coffee with orange flavoring). I was intrigued enough by the idea of a Valencia Orange-flavored liquid stevia that I paid nearly $15 for a 2-oz bottle (supposedly there are 300 servings per bottle).
While it sounds pricey, but it's not so bad when you figure the average cost of a flavored latte at your favorite coffee shop. (In my case, that would be a soy latte, which is even more expensive!) Also, as you can see by the link on the left, it's probably cheaper on Amazon.com, assuming you get the free shipping deal.
SweetLeaf Liquid Stevia Valencia Orange works well, but I suggest you use the upper level of the recommended number of drops (5-8) to flavor your coffee, which definitely cuts down the number of servings it contains. I like the taste; however, please note that stevia is a little more likely to please the palates of those accustomed to artificial sweetener.
I've made as good or better orange or mocha orange "lattes" using Frontier Natural Flavors Alcohol Free Orange flavoring from The Better Health Store plus one packet of Stevia in the Raw, though I have to use 1/4 to 1/2 tsp. rather than 8 to 10 drops.