I work in pathological speech processing/synthesis so I'm unfortunately familiar with your father's position. It really sucks that these people didn't know that archiving their voice would've been useful. I hear snippets that people manage to glean from family videos right after listening to their current voices and it makes me really sad.
On the upside, your father can choose any celebrity he wants to voice him! Tons of celeb data is publicly available (VoxCeleb 1 & 2).
On the upside, your father can choose any celebrity he wants to voice him! Tons of celeb data is publicly available (VoxCeleb 1 & 2).