Find a bike shop with a "stash" of used $5 apiece saddles. Lots of shops have these in bins, and Madison WI is big enough that you can find one of those.
Have your dad select a few of them, and test them on the spot. This exercise could be fun for him.
Buy his top 3 preferences.
Have him ride them. Help him with minute adjustments. He will determine which one of the 3 he prefers.

Repeat the process once he's done a 1,000 miles, or a year later, as by then he'd both require and deserve (meaning that he'd have a better idea of his needs and preferences) something different.

And generally, ignore saddle recommendations given in online forums.