www.ma-tea.com
Sells the commercial South American stuff.
Cheap. The American brands you find in the health food stores are easily 4-5X the price, and I've had the Guyana and a few others, and I prefer the imports.
It's an acquired taste, though. My wife calls it "Dirt Tea" and refuses to drink it. I can drink it iced or hot, though in the beginning I needed a bit of lemon to put in it.
From the above website, Union and Canarias are good brands to start out with, and Rosamonte too.
I drank this today instead of coffee.