No good answer there. I finally switched to a cotton comforter
Tuck in the bottom and sides. Or at the dollar store they sell clips attached to elastic that are made to keep your ironing board cover from slipping off of your ironing board. They're are adjustable. Al you'd need to do is clip one end to the comfortable & the other end to the fitted bottom bed sheet!
They look good but have no practical use because they do not stay on you or bed