I found several online by searching "Nissan Brush Guard". I would highly recommend not buying a brush guard. Since they mount low on the X, any minor front end contact is multiplied by the guard. There are several companies making replacement winch bumpers that look great (Calmini, Hefty, Shrock).
This happened to a member of TheXterra. Scroll down about a quarter of the way. Link:
http://www.thenewx.org/forum/showthread.php?t=43674