I recall a probiotic we always had to get any time I went on antibiotics as a teen. They have it in the pharmacy because it has to be refrigerated, but you don't need an Rx for it and it's not that expensive per bottle. Can't recall the name of the it, but I'm sure the pharmacist would know it. It's a chewable tablet, and he could just take that or the yogurt depending on his mood/hunger that day.
Edit: Acidophilus tablets.
