Many HEB''s have them at the deli.
The best place I've found (don't laugh) is the 24-Hour Shop on 6th Street. The first batch comes out the fryers around 10:00am Monday through Thursday, 8:00am on Fridays. They cook them well done, so they're somewhat tender (for gizzards). Much more edible than HEB's.
I haven't tried Golden Chick, but they have them there, too.