the Phorid flies Genus Pseudacteon
are fairly tiny flies but I don't know if they would be targets for your fly preditors or not perhaps your Land Grant college in Texas can advise, and they would be the most likely source for your phorid flies anyway. The ones in actual use are Pseudacteon tricuspis and Pseudacteon curvatus. Their life cycle is interesting. They reproduce by laying eggs in the body of the ant. The first stage of the larvae eats the heads of ants from the inside out including the brains. With severe brain damage the ant zombies wander about for about two weeks before the heads drop off. The fly pupates in the head section and the cycle starts over again
Solenopsis daguerrei a parasitic ant tries to replace the queen and control the nest other biological controls are also being tried using the flies and ants as vectors to deliver diseases to the ants. The agents include a protozoan, a fungus and a virus. Since there is some concern that these might also attack bees they may not be released for use since the bees are vital to our food chain.