Free or affordable ultrasounds (pregnancy) in Houston?

Hi all, I’m newly pregnant and my supposedly great insurance doesn’t really cover ultrasounds. So my gyno’s office is charging me a crazy amount for it. I just had one ultrasound and now they want to do another one in few days for monitoring. I will probably have to go back to them for it but I would love to find a place where I can get additional ultrasounds if needed for a more affordable cost. I don’t know anyone who has paid as much as I’m paying for mine and I can’t keep doing this regularly. I see some women centers offering ultrasounds for free when I search online, has anyone here been to one and are those legit?