Alas, the gun shows really are the best place in Dallas. We have almost no independent dealers left, and the big stores don't carry used guns.
Bachman Gun & Pawn may have a few occasionally, but don't count on it. McClelland's, ditto.
For a city of this size, there are pitifully few good gun stores.
Can't say about Ft. Worth and the mid-cities.
Bob Bettis mentioned Jackson Armory, near the SMU campus. Nice shop, but high prices, and be sure to check older guns carefully. I've seen a few there that weren't in the best condition, and I think one Webley had functioning issues. But if you have a lot of money, they do have a fine selection of better guns.
T-Star