It's not hard, just time consuming. Generally, open a beer, drink it in one hand, and whisk with the other one, for about an hour. I've never seen it sold, but I haven't really ever looked.
It is such an important part of the gumbo though, and a great technique to learn. (and you will use it a ton) I use equal parts bacon fat and butter to flour in mine, and then let it carmelize until chocolate brown, and I'm usually pretty happy with the end result. Don't be scared, it really is just as simple as stirring over really low heat, for a long time, and like anything,making sure it doesn't burn. Good Luck!