Whole Earth Provision Company has a little bit of gear. There are also three REI locations. I don't know about the Arboretum and Round Rock stores, but the REI downtown carries mostly Black Diamond gear - passive and active. Backwoods is on the way to Reimer's Ranch and Enchanted Rock, if you're headed out that way to climb.
Also, I've got the green thru yellow Black Diamond C4s I'm willing to sell for 20% off, new with tags. I'm out of town, but will be back in Austin the night of Sunday, Jan 2.