My drivers side map pocket is the original one, It was sagging just a little before my easy fix. I pulled the elastic toward the center, one end at a time, then used needle and thread to sew the elastic tight. The extra elastic was then cut off and removed. You can't see where the elastic is sewn because its still inside the pocket and also right next to the snap.
Sorry if that was confusing, I'll try to make it clearer if needed.