What multi-vaccine probiotic can be used in a child after COVID-19?

Good morning, my son has numerous complications after covid -. he does not eat practically salad meat his diet is very poor only cheese yogurt sparingly with fruit because everything does not taste to him to put it mildly. In addition, problems with the stomach bleeding from the anus use ointments recommended by the doctor, unfortunately, there are no clear positive changes. On TV, I've heard about using a multi-vaccine probiotic. Wanting to buy a good I know that it will be more expensive. Please recommend. Thank you in advance for your advice