I broke down and bought a bolt of the fusible stabilizer I use to make fabric postcards. I get a lot of emails asking what I use and where to buy it. I decided to start selling precut 4 x 6 inch pieces specifically for making fabric postcards in my Etsy shop. I think a lot of people overseas have a hard time finding it or so it seems. If you click the link it will take you to my store and the listing I have up for 5 of the rectangles.
As Always Happy Sewing.