AnnR,
Quite a lot of the plaids in my quilt were either on the free table at quilt guild or from Comal Cottons fabric mill in New Braunfels,Texas. The mill closed in either the late 1990s or 2000. They made wonderful 60" wide woven plaids and stripes, under the Mission Valley name. There are some quilt shops that carry good quality woven plaids. I think Moda makes nice plaids, don't know who else does.
Sharon W. aka purplefiend