I tried to carry the PX4 for awhile, and like you said its just too thick to not print. One option might be to use a paddle holster owb, it might help hide it some. I can carry mine like that during the winter. I got the beretta nano as a ccw now, and like it alot. but as you can tell i might be bias towards beretta.
I would try to sell the 9mm outright to get the most out of it, then get a 40 and a ccw. for the right price I'll take the 9mm off your hands!