I went to a high end sewing center and asked for bobbins for one of their brand. They told me their company didn't make that model. I said, "Yes, it is a cast iron one." They gave me the second look of "Why is he even here?" Checked a chart and said, "No, we don't have it.." no suggestions. I was not sad to see that store die.
Most of the letters I write go to food service places, I also write grocery stores for blocking exits. and politicians. I rarely get responses even for serious stuff.