I just drove up to PA to buy mine. Freedom Armory was the closest for me.
BTW, S&W manufactures a few types of 15-22 mags:
25 round black
25 round fde (good luck finding these)
10 round (pinned 25 round)
10 round "short" (not pinned. nice for table work).
Given the frenzy with hi capacity magazine purchases, it might be difficult to find the 25 round'ers.