Houston Health – https://houstonemergency.org/covid-19-vaccines/ You may also follow them on Twitter (@houstonhealth), which is how many have been able to register for an appointment. You do have to act fast though.
Montgomery County – https://coronavirus-response-moco.hub.arcgis.com/pages/vaccinations
Fort Bend County – https://www.fbchealth.org/
Brazoria County – https://us.pomelo.health/brazoriacountytx/login#/
Sam’s Club (you do not need to be a Sam’s club member) – https://www.samsclub.com/pharmacy/immunization?imzType=covid
HEB – https://vaccine.heb.com/