There is nothing in the Penal laws of Texas that prohibit bean bag rounds. There is nothing to do to convert a shotgun to fire bean bag rounds. Remember, you are shooting a weapon that is still considered deadly. Even with the bean bag rounds you would still have to justify using deadly force. Bean bag rounds are not "Non-Lethal", they are less lethal. They can kill (or cause serious bodily injury) (the standard in Texas for a deadly weapon).
IMHO If you can justify shooting a person with a firearm, shoot them with a firearm. Shoot them in a manner that is most likely to stop the behavior that is threatening (Center of mass). Shoot them repeatedly if needed. Shoot them until they alter their behavior (begin cooling to room temperature).