Look on some of the Taxas Hunting forums. There are a lot of listing but also a lot of scams or canned hunts so be careful. Also Huston and Dallas are 250 miles apart so you might want to narrow it down some. I would pick a Hill Country location as it is more scenic. The Helio operations are mostly near the coast as the country is more open and their is a void in the Helicopter market for petrochemical surveying and staff transport currently. Check these out carefully too as several have been fined for shooting on properties with out permission and the clients get popped too.
A call to some of the rural chambers of commerce can pan out and even better look up the regional game warden as they know where the problem areas are and the scammers.
There is a Hog Dog competition in Halletsville Tx. and also a hog breeder (as if we didn't have enough already) who might have information on hunts.
I see listings in the paper and on Craigslist but Caveat Emptor. But you could do an in search of listing and then be really thorough in checking out the responses.
I have projects going in both Houston and dallas and have to travel in between them.
I'd like find a personal recommendation, I've seen way to many bad operators.