I bought a babka at Central Market on Lamar, I think it was sometime last year. It was okay but nothing wonderful. I, like you, don't know bupkis about babka, so I can't tell you whether it was representative of a good one or not.
HEB off of Far West has a Kosher Dept. There's a pretty good cinnamon babka there around the holidays. It is packaged in a orange paper tray inside a plastic bag. I believe the manufacturer is Greens. The chocolate one, not so good. HEB 7025 Village Ctr Dr. Austin, TX 78731