When all else fails, I look for an inexpensive cotton sheet. I haven't done that in a while and just wonder if there are any out there anymore? fyi....When Hancock's was still in business, I bought the wide backings by the bolt when they were on sale. I am slowly but surely running out. I will have to start watching for sales. I H.A.T.E. sewing the backings together for the kings.
Edited to add: I have never bought from Thousands of Bolts but certainly will if I need a large backing.
https://www.thousandsofbolts.com/ind...category_ID=26