There is a kit to put a new style boot on that.

Or atleast there used to be a kit available.    Hog Slat had them I think.


It contained two pieces of sheet metal that reduced the size of the opening in the bottom of the bin down from 22" to the more standard 16"


Here's a link for the pieces of sheet metal.       https://farmerboyag.com/feeders-accessories/feed-bins-parts/feed-bin-parts-accessories/