Does anyone know any online retailer selling the S&W M&P uppers. Specifically, I want to purchase one of the piston models but I can't find a local dealer that seems interested in looking for one for me. I have an OR model and I've got dillusions about setting up a Pelican case with a complete set of both DGI and Piston uppers decked out with different optic setups, accesories, etc. Kind of my dream AR kit. Thanks for any help.