How to save on-the-go naps

Have you found yourself in this scenario? You and the baby go out to run a few quick errands between awake windows with the goal to make it home in time for a nap. All is going as planned, you look at your watch and see you will make it just in time. You are 5 minutes away; you look in the back seat to check on your little one and you notice she is sound asleep! The panic sets in and you think to yourself “Oh dear, what do I do now?”.