http://www.hartnagels.com/pvc.htm
I am making my own portable frame for taking camping with me ~ mainly to keep the quilt off the ground for tying, and the kids can help while we chill on the deck ~ so we're building from 1" PVC, and are ordering 1.25" and 1.5 inch clamps so I have flexibility depending on thickness of quilt.
(I am building a unique angled skinny design that is friendly to my arthritis and sciatica :) )