They were in stock at Midway recently so I would assume that your chances are good with S&W right now. Give them a call and see what they say, if you want to go with factory.

I've only used Wolff in a few of my mags so far, but no problems at all. They are cheaper than S&W if you buy them in the 10-packs too, which was the selling point for me.

*Forgot to say that I think the extra power springs would be good in shorter-cycling guns like the CS9 and 4040PD. Basing this off of some advice of Fastbolt on the CS9 and my own experiences with used 4040 mags not locking the slide back.