Where to get PCR Test in Houston to fly into Canada?

Hello all,

My family members are flying into Houston tomorrow from Toronto due to a death in our family. I was able to get them an antigen test so they can get on their flight tomorrow

On the flight back, Canada requires a PCR test. I am wondering where I can get them tested? Is there a facility at the airport, if so any resources would be super helpful. They are flying air Canada if that helps.

Thanks in advance for your help!