I haven't seen any new Winchester brass for the 7 Rem mag in years. This explanation from Midway sums it up:
''This product is only manufactured periodically, often on inconsistent intervals. Please use our "Notify Me" feature to receive an email alert as soon as the product arrives.''
Best you can do is try to find a private sale on Gunbroker or similar site. If I were going to once again own a 7 Rem mag I would use Norma brass. At least it is available and is of good quality.
Why should Remington and Winchester offer brass in this time of high demand when loaded ammo will yield them a much higher profit?