Ive ordered from Mulberry Farms many times and have really liked dealing with them. I usually get the horns and a few other feeders when I order. They are a site sponsor here.
At the top right-hand of your screen click on view our sponsors. several places to check out. I got my latest batch from Great Lakes Hornworms but have used Mulberry and some others. I'm partial to Great Lakes and Mulberry lately but location and shipping could be factors.