I've conducted a few "experiments" with these materials.
- Disposable ear plugs (from Harbour Freight Tools): work, but are a bit too "squishy" for my taste.
- "Marshmallow" shaped foam from Michaels: I cut them in thirds. Consistency was a bit too stiff, and I had
trouble putting the pins in the middle. Result: pricked fingers. :-(
So I broke down and bought the real Pinmoors. Should have done that to start with I guess. LOL.