So, update. I tried the Specialized insoles but they didn't fit right. I wound up buying some Shimano insoles that are heat-molded to your feet. You do the heating and molding at the LBS, using an oven supplied by Shimano (apparently their shoes also require heat molding).

They seemed fine at first, but part-way through my first long ride with them my calves started to cramp. And then my calves cramped during my next long ride in them. And again last night during a shorter ride.

I think the arch support is too pronounced. Which is kinda weird, since they were totally flat before being heated, and it's not like I used someone else's feet to mold them when they came out of the oven.

Anyway, the LBS manager said they could be heated and molded a total of three times, so I'm going to take them back and try molding them again.