We bought one this last spring from an awning manufacturer who said, "Oh, yeah. We do those all the time." It hasn't been good. It's in need of major repairs after one season, so before you pay someone to make you one, get a recommendation from someone who knows the folks who'll do it, if at all possible.
Here's an option we've considered (this guy apparently makes 'em for less than we paid, for sure):
http://www.catsail.com/class5822.htm