My sister-in-law asked me to make a nap quilt for her grand daughter, with weight to it, to help her nap at pre school. I did a little reading on line, and realized it was not much different than fabric bead-stuffed "frogs" we use in the Neonatal Intensive Care for newborns suffering pain, or drug withdrawl, that simply provide a little weight on their bodies and console them.
The poly, washable beads were not difficult to purchase online (I found them on ETSY) and made a simple flannel blanket that I left open on 2 sides when I turned it right side out. I top stitched vertically, top stitched a line right down the middle horizontally. I decided on the weight (10% of body weight plus 1 pound) and used a funnel to load one row at a time. Then to the machine to close up that row, and on to the next.
I left the very edges unstuffed, figuring the weight would be best utilized if concentrated in the center.
My cost for materials was around $15 for beads and flannel (Flannel on sale; it used 3 1/2 yard cuts for the blocks and a 1 1/2 yard piece for the back.) and the beads. I have been told they can cost hundreds to purchase.