Whoops, sorry about that. According to Play N' Trade's storefinder, the only one left in Houston is over near Sugar Land on the opposite side of the city from Spring. That sucks. Which just leaves the one in Montgomery (just south of Lake Conroe).
If you've got a car, a GPS, and most of a day to kill, you might drive up to Bryan and College Station. I've heard that there's some decent retro game stores there. FX Game Exchange for one. The guys at the FX Game Exchange in Waco told me that the location there has a lot of classic stuff.