Do you only need to make one 9 patch block?
Will you be making Blocks monthly? If so - Do you want the same material in every block?
I hope my math is right!
You could buy fat quarters and if I calculated right if the fat quarter is 18 x 22 you would get 4 - 8" blocks
1/4 of a yard WOF is 9" wide and you would get 4 - 8" blocks