Grandma called this "Cutting off your nose to spite your face."
Stock barrel $85 at Midway is what I would do. I LIKE my plastic M&P and an officious flunky is not going to keep me from it.
He could do that, but then he'd have a 4.25" barrel in a slide designed for a 5.0" barrel.
S&W has quietly discontinued 5.0" 40 S&W models due to low sales. There's a reason that CDNN has been selling FDE 5" slides for $50-60 on ebay for the past several months. They clearly bought up S&W's excess inventory. I bought one of the slides for under $50 with an eBay coupon, then realized that 5" 40 S&W barrels were unobtanium.
40 S&W has become a niche caliber. It still outsells .38 Special in the US, but 9x19 outsells it by over 25 to 1. That steady demand for ammunition is not indictative of new pistol sales; one of the big problems for new .40 S&W pistol sales is that LE agencies have rapidly switched back to 9mm over the past decade. This means that new pistols are competing with lightly-used LE trade-ins.
Man, I wish other gun manufacturers used the m&p magazine pattern cause my state is going total commie and I have a ton of full capacity mags. Guess I'll be looking at glock and CZ pattern stuff from now on. Sad to see them go but it must be done. Good luck to everyone else with the aging of their guns and hopefully finding parts.
Glock and CZ aren't going to solve any theoretical parts issues for you. Glock has announced to dealers that everything in .40 S&W is getting discontinued, and it remains to be seen if there will be any replacement models.
Even before then, .40 S&W Glocks were down to batch production when enough LE agencies made orders for them. Some
Illinois State Police officers commissioned 100 year anniversary commemorative Glock 17s, which is somewhat humorous because the ISP has never issued a Glock in 9mm. However, there wasn't going to be a .40 S&W batch anytime soon, so they settled for G17s.
As for CZ... there are legions of Shadow 2 OR owners who can tell you just how non-existent extended safeties can be for months at a time. IIRC, the only current production 40 S&W CZ is the TS2, which clearly isn't designed for carry at 48.5 oz unloaded and a <2 lb trigger.
The best outcome that S&W could plausibly make for you is replace the pistol with a current production pistol in a different caliber, or a different 40 S&W in 4.25". I've met a police officer who shot his 45xx enough to crack the frame; S&W replaced it with an M&P 2.0 in 45 ACP, as 45xx production had stopped ~20 years earlier.