Check out UBG, we have a pretty good collection of his work and he makes good gear for righty's and lefty's.

Another guy I've been happy with is Desibens Gun Leather (DGL), he lists the PX4 Storm.

I also have two new holsters from Alessi that I'm pleased with.

Almost any good holster maker offers left handed models, and all three that I've listed have the PX4 in their model lists.

I use a Master's Leather Holster for my PX4. I am right handed but they make a left handed holster.

MASTER'S Leather PANCAKE Holster - Open Top

You don't say which storm PX4 you are reffering to, full, compact or sub-compact. I have a PX$ compact and am left handed and bought and use two holster which I am very happy with. One is from sideguardholsters.com which was custom made for the PX4 with a "lasermax" laser mounted on the rail and with exotic trim. His work is outstanding and there is a long waiting period but it is orht it. The other holster is frm hiddenhybridholster.com and the model i got is HHHC1 and I am very please with the fit and quality of workmanship. Good luck with your new PX4

I had Holsterpro make me a Model 722 for my PX4 compact to wear on my left hip and also purchased a right-handed Nate Squared Tactical IWB in right hand version that I wear at 5-6 oclock thus enabling me to draw left-handed with palm out from IWB...really comfy IWB...will review the HolsterPro as have yet to recieve it..only been ordered a week