My father is 95 and has worn hearing aides for quite awhile. He goes to an audiologist recommended to him by his
family doctor. He wears a hearing aide in both ears and it is a tiny tube that goes into the ear but the mechanism fits behind the ear. He said it is a vast improvement over the one that was in the ear. It is operated with a remote control
He has all his marbles and is quite sharp. Check with your family doctor or a doctor you can trust that you like and ask for a recommendation. Also an EENT doc would be able to recommend as well. Does your mother in law have one?