@bookreader1 - Not familiar with recliner chairs with built-in heat. Is your father in a care facility? If so, I would ask them if heated chairs are allowed (possible safety concerns?) and if they have any recommendations. Sometimes PT or nursing staff have relevant input. Someone else can likely add experience with that type of chair.
Does your father have any cognitive challenges that would make it hard for him to learn the controls? I wonder if there would be any advantage to separating the heat component from the recliner itself. That way, if it becomes too complicated to use the heat feature appropriately, it can just be removed. If it is possible for him to try chairs with you for size, comfort, features and skill in operating it, it will be extremely helpful. My frail mother without dementia thought a lift chair would be great. When we went to try one out, she could not get past the sensation of being tipped too far forward into a fall: the issue was her weakness, not a failing of the chair. My father with advancing memory loss loved his electric recliner and never lost the ability to operate it. It is a highly individualized thing.
The number of brick and mortar places that sell medical hard goods and have chairs on display for test-driving have diminished rapidly around here. Perhaps people are ordering on-line. I was glad for the stores when I was tending my parents and even myself with leg fractures.
Best with the search.