Scroll along the units using the left/right arrows so the unit icon is in a different place, then the popup will show further along the map screen and not always but most of the time you can then see the unit in question whilst the popup is showing.
Otherwise just quickly use process of elimination from what troops you can see to determine who fights next.
I have found this irritating myself when the popup covers the troop on the map you are trying to look at and instantly see who fights next. But it is easy to get around by scrolling or using elimination.