Why not design your own? Barbara Chainey's "Essential Quilter" has a section on how to. Also, Karen McTavish machine quilts some gorgeous whole cloths. Her book on "Whitework" is out of print, but you could probably find it at your local library. I read on another site that this book is quite expensive from some of the used book sellers. I happen to have it and while there are some beautiful quilts I didn't find much in the way of "how to." Of course, I'm a hand quilter and perhaps I missed something. Some years ago I bought a throw size preprinted wholecloth, but found the fabric to be extremely thin. I don't remember the brand name, but thought it was Benartex. I have at present a pattern drawn out on paper and the fabric on a shelf. I have a couple of projects to finish before I transfer it to fabric. A king size whole cloth and a strippy are on my bucket list.
Having said all that, if you google, Benartex Whole Cloth quilts, you will find sources from which to purchase.