ISO Blue Bell Ice Cream in the Triangle
I would check either your local Walmart or Walgreen's. I have not seen the blackberry crumble in my area which is Rockingham but I have been able to get many different flavors in Rockingham, Marion and Boone at various times before.
Side note: my personal favorite is Pralines n Cream.
You might be interested in an article from the Houston Chronicle this morning. Bluebell should be getting more available for you.
I'm guessing that the blackberry, like many Bluebell flavors is seasonal, and it might just be gone till next summer. They have us trained to get them while we can :-)