Check the USMS website, I know there's a Lifetime fitness there that has master swim. I traveled there maybe 2 years ago and was able to get a swim in at Katy HS. I emailed the contact person on the USMS website and actually got an email back. it was a different contact person a couple years ago but I'd give that a shot. The nice thing was since it was at a High School there was no charge. There was also youth swimming at the time but the masters group we pretty small and only needed 2 lanes. They had pull buoys, paddles & kickboards so all I needed was my suit and goggles.

I don't know anything about their program but Katy Aquatics has a masters program.

Katy Mastes or Fleet masters. Use your google machine to find times...