What kind of P250 do you have? I have a Blackhawk SERPA paddle holster, and two 15 rd mags available. I had the one with the round accessory rail. PM if you have questions or would like them, I'm sure I could work out a good deal for you.
As far as I know now, the BlackHawk SERPAs will only fit the frames with the rounded rails. Galco makes a few holsters for it. DeSantis makes a nice leather holster that is being issued to the Federal Air Marshals carrying the P250s. Safariland makes several good duty holsters. Any holster that fits the square rail (Picatinny?) version will also hold the rounded-rail version.
What kind of holster are you looking for (e.g. iwb...)? Also, full size or compact? Don Hume has some decent IWB holsters and I found that the IWB (non thumb brake) for a Glock 21SF fit the full size .45.