Solid Black Patio Chair Cushion

In past years Target sold outdoor chair cushions that had one rounded edge like the attached image. I have a few old ones that are kind of mashed, so it's hard to provide exact dimensions. My local Target doesn't have them this year. I need a black cushion. It won't be used for seating. A gizmo I built requires a rugged, outdoor cushion. The Target cushions were about 3 to 4 inches thick. They were stuffed with a firm polyester batting. (Very cheap cushions use the lowest grade foam rubber.) If I remember correctly, the Target price was $18.00. They lasted a couple of years, which was ok for an $18.00 cushion.