Have you considered not giving him milk at all? There is no need for him to have milk of any sort once he's 12 months, as long as he's getting the nutrients he needs from his diet. A dietician who specialises in allergy and intolerance (and there are many of them!) could assist you with a diet plan to make sure he's getting all he needs.

Personally, if it was me, I'd prefer this option to toddler milk. Toddler milk does not have all the nutrients he needs, and often it fills them up enough that they don't enough other foods.

If you are interested in this approach, you can search for dieticians by specialty on the Australian Dietician's Association website.