I have a regular 3913 (not the Lady Smith or “NL” versions). Great gun, but original mags are very hard to find now, and when you find any used ones for sale, they can be very pricey. I believe they take the same mags as the CS9 and the 908, but those are no longer made, either. ProMag sells new mags that fit, though, but I’ve read conflicting reviews on their reliability. I have a ProMag for it but haven’t tried it out yet. Even if the ProMag works, I would only use it for range use, though, and not rely on it for carry use.
As for parts and springs, Brownell’s still sells some, but a few items appear to be sold out:
https://www.brownells.com/parts/Smith+zzxzz+Wesson/3913/index.htm
Holsters are harder to find compared to the more popular carry models, but the older holster makers should still have molds for them. Just make sure you specify yours is the “NL” since I believe the NL dust covers are different from the regular 3913 dust covers. So there may be fitment issues between the two. I honestly don’t know, though, but thought I’d mention that just in case.
Someone mentioned they’re light enough to carry. I still carry mine on occasion, but it’s obviously heavier than my Shield Plus but lighter than my 5” steel 1911.
If I already didn’t have a 3913 and were looking into a 3rd gen S&W, I would absolutely consider buying that one for $499, even if it just has one mag. If you do decide to get it, post pics and give us a range report!