Gildan has a great line of military themed T shirts in KMart stores this year. The marine corps shirt is standard fire truck red with gold "USMC" lettering.
i suggest you carry them in larger sizes, though, as some of the marines can be pretty big guys, and tall. Larger than life, really. It just thrills me that KMart thought to have such a sharp display rack dedicated to these shirts.
Related shirts include "Hero" , "USAF", and two different "ARMY" shirts. That's right! the Army is twice as good! Hoo-rah!