Hi Diane37
I don’t know the prices or the exact details off the top of my head but there are a number of other cotton/wool quilted options in the component post here.
A quilted cover has fabric on top and another layer of fabric as a backing and I believe that the top fabric is a stretch knit but the backing may not be but they would be able to give you much more specific information about it than I can.
You are down to the type of changes where your own trial and error and experience will be the only way to really know which combination will be the “best possible” for you but I’m grateful that you are sharing your experiences with the rest of the forum and I think that I and many of the members here that are following your topic will be cheering right along with you when you finally hit the combination that works the way you want it to 
Phoenix