There is no reason for him to have artificial breast milk at this stage, he should be getting his nutrients from foods.
What about hemp milk? I find Pacific's to be the best as they don't put in oils and cane sugars. They sweeten with brown rice. It's also chock full of protein and all the omegas. That being said, does he really need a 'milk'?
Milk allergies don't only run in your family, most people can't tolerate cow's breast milk because they are not cows, don't have 4 chambers to their stomach, etc. It's just most of society has physical problems they ignore or think are normal.
Are you worried about nutrition? Once a child is weans from his/her mother's breast, there is NO health reason to get the lactational secretions of another mammal. Want calcium? give him lots of green leafy veggies and sesame seeds (or tahini). Want protein? give him veggies, fresh whole grains (quinoa is a complete protein with many other vitamins and minerals), beans, legumes, nuts and seeds.
What he should be drinking is water. Flushes out toxins and doesn't lead to diabetes, obesity, cancer, tumors, cysts, allergies, etc.
I also suggest getting rid of your pediatrician and seeking out some advice on your own which it seems you are doing.