Formula to milk

Ra

My son is not 12 months and 4 days old. He was on nutramigen basically since he was 3 months old. I can't find any of the toddler nutramigen in any stores near me and I can find the small cans of it online but I have no desire to spend that much. My pediatrician said whole fat milk is fine for him but he won't drink it. I have no idea what I'm supposed to be doing here. Does anyone have any suggestions as to what I can do next?