You can get new mags for it at Midway USA for $18.73 ea. They also have 9 round mags that will fit it for $10 more.
Never mind, those were Pro mags.
These claim to be factory original stainless 9 round mags for $28.53 ea
Smith & Wesson Mag S&W 39 439 539 639 909 952 3904 3906 3944 3946 9mm