Looks like there are several makes and models, all slightly different. I guess I would measure her unit and make an open tote. Here's a video on measuring and making a sewing machine cover. You can use this cover upside down for a basic bag, then add handles, and a ribbon to tie the top. As far as openings for the buttons, you have several options. You can just cut a hole in the appropriate place and bind the opening, or use an oversize curtain grommet. They come in different sizes and colors. Here's an example:
http://www.joann.com/dritz-home-curt...rd1002400.html