I have a stuff sack that at one time came with a tent, long and maybe a foot in diameter. Into the sack I stuff my PFD, which will become my pillow. Using the extra sack material that is longer than what is required to hold the pfd, I gather the extra something like the ends of a sausage, tie it closed and loop the rope around my sleeping pads. (I use two pads to cushion these old bones.) Granted the sleeping pads will flex in under the rope but with two or three loops I find the pillow stays put. Then the next morning the pads will go into the ex-tent stuff sack for travel.
Works for me anyway.
Best Wishes, Rob