The list of At-Large warranted heralds can be found in the services portal, by clicking on “Groups” on the left-hand sidebar, and then “Officer Directory”. Then, in the top search bar, under the spyglass, select “Office Name” and type “At Large Heralds” into the search bar.
The list of currently warranted At-Large heralds can be seen in this direct link. To become warranted as an At-Large herald, you must submit a herald’s report at least yearly.