I.F.
Oh, I know how you feel! My 4 year old only wants water, will not drink milk. I keep trying but in the meantime I found a good supplement: Multi Vitamin with Minerals Liquid Supplement for Children. It has 50% DV of calcium (in 2 tsp.) I mix it with water - makes the water pink but my son is fine with it. I got it on-line at either Doctor's Trust or Vitacost, one of those.
Good luck!