Hi,
The official NFL store are unlikely to get new Reebok stock, since Nike are taking over. The same will apply to most official outlets. Your best bet is to check eBay. If you are just looking for a screen printed replica, these aren't faked, so you should be able to find a legit one in a youth size for a good price. Beware of anything with stitched numbers, if you are new to jerseys though. Most of these on eBay are fake.