What a coincidence. I also like my Bersa Thunder 380 and enjoy shooting it. I even carry it!
Depending on how I carry it, I often use the optional 9-round mag for a capacity of 10 rounds, with a spare 7-round mag in a pocket. I use Buffalo Bore .380 ammo labeled "+P" (yes, I know there is no such thing officially) 95gr JHP. They also make a 100gr hard-cast flat-nosed lead if you want to go for non-expanding with plenty of penetration.
Keep in mind that .380, 9mm, .38 special, and .357 magnum all punch an identical-sized hole if the round doesn't expand, so it may be just as good as the .38 if heavy clothing plugs a JHP.
Hard to decide if five .38s would be better than ten .380s until after the gunfight.