Holy cow! Just checked several area stores (Finger Lakes in NY) as well as stores near our winter home in FL. NONE of them have Stay-Flo in stock. A half gallon is $23 to be shipped, or $40 for 2 w/ free shipping! Amazon offers a dry starch that is "pre-gelatinized", makes 3 gallons, no boiling needed, the brand is Simpli Starch as well as another laundry starch liquid concentrate, Linit, for $16.
I wonder if this is a temporary blip in the supply. How long does this stuff keep, prior to mixing? It's still available at School Specialty for $7.49. You have to set up an account, and shipping is $11.95 unless you spend over $69. The bottle on my shelf has no expiry date on it, making me think it would keep for quite some time. They also sell newsprint at a good price, if you are into foundation paper piecing.