The Walther P99 came out after the start of the 1994 Ban On Cosmetic Features.
And it didn't originally come in .40 S&W caliber.
So I highly doubt you will find any "pre-ban" .40 S&W P99 magazines.
However, you will find normal capacity 12 round magazines for the .40 S&W P99 at several vendors, including CDNN.
Google is your friend.