Here are llinks to many of the suppliers we discussed over the course.
Handweavers Studio- has a variety of yarns and will wind small quantities.
My Fine Weaving Yarn- Cotton, Bamboo, Tencel, and probably more!
JC Rennie- many of the very chunky wool yarns used are JC Rennie's 2/9 Shetland
Uppingham a wide variety, but often limited quantities.