If you're not picky about the looks...you can make a 4.3 fit a serpa. You need to cut off the end of the holster. Even then the end of the pistol will stick out a bit...which looks kind of goofy.
5.1 fits much better (although you need to mod the trigger guard...or swap the grip).
A generic nylon holster might fit the bill until you figure out which one works for certain.