Thanks Chris. I'll keep John in mind.  It seems odd that a replacement for such a critical item costs $20. The cost of the part is insignificant compared to the grief a failed switch can cause, especially in a livestock watering system. There must be a made-in-USA industrial version available somewhere.

edit to add: There is a heavy duty Square D switch available, 9013GSB (Nema 3 Outdoor) or 9013GSG (Nema 1) that I just ordered which is a commercial grade switch. This is much heavier duty than the standard grade (Square D 9013 F series or similar)