I wouldn't trade 7 or 8 rounds of 9mm +P in a light, flat, easy to carry pistol with real sights and a decent trigger for any 5 shot snubby with a crappy 10 lb trigger and barely-there sights.
There are considerations that should be more important than a couple of ounces of weight. A carry gun should be more comforting than comfortable.
How long will it be before you decide that your new lightweight .38 is a little too bulky and heavy, considering the pocket .380s that are much smaller and lighter?
Save your money. Buy more 9mm ammo and practice with your LC9. You've already got a Charter .38. Are you really going to spend $350-400 to buy the same thing you already have, minus a couple of ounces of weight? Might be cheaper to cinch up your belt another notch.
Pocket .380s are the devil!!!!