Welcome from Idaho! Can't help with the weighted part, but check out
http://www.allpeoplequilt.com/quilt-...ig-block-duvet for a free pattern called "Sweet Slumber Duvet Cover". I made one for my mom and it is simple and easy to do. It will give you an idea for the duvet at no cost. Good luck with your summer sewing and beyond! Don't forget to post finished photos, would love to see what you decide on.