If you're near the Memorial City mall, there is a good shirt shop there (not hot topic). It's near target. Got a GnR shirt there for an 80's party a few months ago.
I try to always avoid shopping malls, so I completely forgot about the stores mentioned. That said, I wasted plenty of time over the weekend looking up and down Westheimer with no luck. Thanks for the recs; I'll check 'em out.
Oooooohhhh...look everyone! We're being graced by the presence of the cultural sophisticate elites of high society who only wear G'N'R shirts to be ironic! Well la-tee-freakin'-dah!!!