Fabric Shack will cut 1/3 yard, you put .33 in the yardage box. For that matter, they'll cut 1/8 of a yard (.125).
Prairie Point Junction has the same decimal system for yardage, so you can put .33 in there, too (or presumably, .125).
Rossville Quilts and Little Red Hen sell FQ.
Quilts 'n Gifts, L'il Red Hen and Wash Tub quilts sell 1/4 yards.
I try to support the on-line stores that will cut smaller amounts, as I really appreciate it!