Google/Bing 'weighted blanket'. I can't find my links otherwise I'd send them to you. What I have read you should use poly beads. Jo-anns, Hobby Lobby, Michaels has them in 4 pound bags. They should be childs weight minus 5-8 pounds. Some make bags and put into a shell, others sew them into a shell like the puffy quilts (only not as puffy). They need to be washable. Others use beans, or rice, but these have to be removable from the covers to be washed.
The idea behind is that Autistic people (helps Autistic adults too) need to have a sensory out let and the weight gives that to them.
What I have read they are remarkable for helping.