For dairy choices, try goat milk (either powdered or not; probably available at your Whole Foods-type store). Or try powdered whole milk - I think Nestle has some; we bought ours at a local ethic (Somali-run) grocery. Powdered milk, I think because of the heat used to dehydrate it, tastes a little sweeter than regular (non-dehydrated milk).
Soy, almond, and rice milk are alternatives, but a lot of them tend to be heavy on the sugar, and don't have the same nutrients, so be a label-reader and compare them. Also, make sure that if you choose one of these, it has vitamins/minerals added. Protein and calcium, and some fat and minerals/vitamins are the big things that cow milk (and goat milk) offer to little growing bodies.
There are lots of cultures that don't use milk (of any kind), and just drink water & get their nutritional needs met through food. You might want to get a good multivitamin (we use Tri-Vy-Sol w/o iron, per ped. recommendation, since our little one was about 1 month old; that is in addition to his regular intake of breastmilk as an infant, as well as now as a toddler eating solid food & drinking about 4 oz of milk per day).
I think that there are also "toddler formulas" out there; we didn't look into them, but I would guess that might be an alternative, though probably more expensive than cow's milk.
You also might try mixing his formula and milk -- giving the same amount of formula per whatever recommendations you're following, over the course of the day, but adding into that some of his daily milk ration. Over time, gradually decrease the amount of formula (feeding separately if needed); this might accustom him to the taste of the milk more gradually.