Low-Cost Vet opened on Christmas Eve?

Does anyone know of any low-cost veterinarians in Houston that are open on 12/24/2021? I am not looking to go to an emergency center and spend more than I can afford. My regular vet, Gulfgate Animal Hospital in southeast Houston, is closed until Monday. My 9-year-old 17 lb small terrier is experiencing diarrhea. I can't wait till Monday. He was in great spirits all day. Unfortunately late tonight, he had 4 very wet stool accidents. I should have gone today, but my vet had no availability.