Buy a 4.5" M&P45. Add an Apex DCAEK and Trijicon night sights and you have the same thing with a better trigger. Or send your gun into the S&W pro shop and have trigger done.
During my factory tour I asked about the longslide 45. Guy I asked said it is in the works, although he may have just told me what I wanted to hear. Saw some single stack M&P 9 slides being machined. Wish the tour was longer, I could spend a full day in there easily...