Sta-Flo liquid starch is normally in regular grocery stores. It is made by Purex and mostly found in the laundry detergent area.
My recipe: = 1/3 cup Vodka (doesn't matter if its made with grain or with potatoes) , 3 cups water.
Shake (no heat needed). Add 1/2 cup liquid starch if desired. Good luck!
Oh, you are in Portland - I'm up in Battle Ground, WA and shop at Fred Meyers!