One of the front plastic feet of my household stairs, 5 steps, of “Excelsior” brand (I think these are manufactured by Altrex), had disappeared, and the other one seemed to be on the way out, too. I modeled and printed two replacement feet. This fits their 40 x 20 mm rectangular rounded (5mm radius) profiles, and may fit other ladders using similar profiles as well.

I printed these in TPU 95A for better surface grip, but e.g. PETG should work well too. Just snap on, they should be a tight fit.