What's the best multivitamin to take when on omeprazole and domperidone?

No Evidence Any: Multivitamins are a big business with lots of marketing to sell low cost to produce products. Vitamins widely available in most foods of natural origin (reason we have not maintained all genes/proteins to make) & most discovered in unusual situations in which large numbers of people on very restricted foods for long periods. No evidence of any health benefit for people eating a variety of foods.