Ever hear of back-supporting inserts for metal folding chairs?

When I’m fated to sit on a standard metal (or padded) folding chair, I end up with a sore back. The whole lower back area is simply open; there’s only minimal support in the shoulder blade region.

Is there such a thing as an insert for lower back support with a folding chair? It’s a wide opening; cushions fall right through. My searches have turned up nothing.