I also was looking on the internet for one a few days ago. I also need to make actually two. I found some different ones, but at the moment couldn't find my patterns, but one lady said she measured hers by how tall, and how wide, and then the piece that would go over the sides and top, and she added 2 inches to those measurements so it would fit loose enough when she went to put it over her machine. I haven't made one so I don't know how exact that is. I hope you find one that will work for you.