I do indeed prefer the 7 round mag with the pinky extension.
As for holsters, for pocket carry
the Sig Sauer one for the P238 does indeed fit the P938. It's not an exact fit, but good enough. I currently use the one that came with the Crimson Trace Laserguard (moved it over from the P238). For belt carry I don't have any particular recommendations; IMO, if I'm going to carry a gun on my belt I'm carrying a rather larger one with more capacity/larger caliber.