If I understand you correctly, you'd like perkier, lifted breasts without a drop in volume. This can be accomplished in 1 of 2 ways. The first is repeat mastopexy. How extensive the procedure is depends on how much needs to be done. If the areolas are pointing downward, virtually the entire old incision (or at least the portion around the areola and the vertical portion) would need to be re-incised. The horizontal incision may or may not need to be recut, depending on how much excess breast skin you have and how the pedicle (tissue supporting the blood supply to the nipple and areola) was designed at your last procedure.
The other possibility, depending on your desire to restore volume preferentially to the upper pole of the breast, is placement of a breast implant. This sounds somewhat paradoxical, given that you recently underwent a breast reduction, but if you lost a significant amont of volume from the upper breast with your 40 lb. wt loss, this may be the only way to restore it.
I recommend consultation with a board-certified plastic surgeon, particularly one with experience in secondary breast lifts/reductions. Hope this helps. Best of luck.