Look into Uncle mikes for kydex mag holders in my opinion. Those are what I depend on actually for my Glocks and my SIG (single stack). You'll need to search for your P345, but I'd bet they make one for your application. I like their modularity. I've carried these OWB and IWB for any and all.
Uncle Mikes 50371 Kydex Single Mag Case Single Row / Holsters & Accessories - Magazine Pouches / Uncle Mikes 50371
By the way...welcome to the forum (I noticed this was your first post)!