The current 3906 magazines, right from S&W, will also work in your pistol without issue. $42 plus shipping, and I think you can buy less than $200 worth with only a $5 export fee from S&W, though these things all change weekly.
Numrich has sold me Promag and worse in the past, they don't seem to discriminate. You can get factory original mags, new, used, aftermarket, or anything else. Sometimes the wrong mag, just to keep you on your toes. They're a great source, regardless, but no, when then send the wrong mag, they do not credit you the $25 export fee so excellently described by prproulx. If you can find someone to ask, they may be able to tell you what it is you will actually get this week, and that would be well worthwhile before laying down your hard-earned cash.
Try advertising a W.T.B. in the parts & bits section of the Equipment Exchange right here...