Replacement feet for an extension ladder. I can
get them online at Werner, but was hoping to
find them locally. No luck at HD or Lowes. Anyone
ever bought them in a store?

I've never seen the feet for any kind of a ladder available separately in any store. This is such a specialized item that your only avenue is to order them from the manufacturer as a part for your ladder.

I've never seen the screw-in feet for fridges, stoves, washers or dryers available as anything but parts from the manufacturer either, so that pretty much tells you how interested retail stores would be in using up valuable shelf space to stock an item like ladder feet that simply wouldn't sell sufficiently to justify keeping them in stock. Stores like Home Depot, Lowes or Menards won't keep items in stock that don't earn their keep by selling quickly.