All the first season boots had that "cuban heel", but that sole looks unique to the captain. A few guest actors have commented that Mr. Shatner had few concerns about looking too short next to them, to the point where he refused to be in the same frame as taller actors.
I've just ordered a pair of the 1st season style from a new company...will let you know how they turn out.
It was stated in STAR TREK: THE INSIDE STORY that Shatner wore lifts so that he'd be taller.