Where can I get an authentic San Francisco 49er jersey?

Where can I get an authentic cheap San Francisco 49er jerseys?

I'm going crazy trying to find an AUTHENTIC cheap jersey for either woman's sizes or youth's. Please help.
THANKS!

NFLshop.com as long as it has the NFL logo at the neck its authentic. Models has authentic jerseys too but your best bet is NFLshop.com most other stores are rip offs. If it's authentic and docent have a retired or traded player and is under 70 or 80 bucks you also know it's a rip off.