Chevrolet horn button screws

[rob love]

Believe it or not, McMaster Carr will not export to Canada (this may have changed but I have not heard otherwise).
When I find boxes or jars of old steel, non plated, slot drive screws at the surplus places, I buy them. My inventory is decent enough that I rarely have to order them these days. And when I do need old time fasteners, Blacksmiths bolt and rivet supply in the US is my go-to place. They do not sell torx, robertson, phillips, their hardware is non-plated and usually chemically blackened. https://www.blacksmithbolt.com/