I don't know if you called Plainfield Shooting Supply or not. I was in there yesterday and they had more handgun stock that I had seen in other shops lately. I wasn't looking at M&P's though so I can't help you there.
The sand burr in rochester does. I was there Tuesday and they had some, I cant remember the price, but i know it was under msrp. give them a call Sand Burr Gun Ranch
plainfield shooting supply had one in stock a couple days ago for 479$, there a some on gunbroker for a decent price, and there were a couple other shops that i called looking for one with an external thumb safety that had them in stock but i don't remember there name. i just googled Indiana Gun Shops and started calling.
As for reasonable price..with the demand so high you might just have to pay a few extra $ now or wait this mess out and get a good price later. Quoting someone else from a week ago on here..........just wait til all the wives see the credit card bills next month and there will be a lot of guns listed soon! lol
I just bought a M&P Shield 9mm from J. Osbornes Gunsmithing and Firearms in Virginia for $500 shipped. It cost me another $20 for the FFL fees. John is a great guy, he also gave me a great deal on an AR-15 last week. Its not here just yet but its on its way.