Iron stores don't run out after 6mos! Thats such an old wives tale! They may decrease, but thye never run out as long as mom has a healthy diet and is getting even a small amount of sunlight a week.
Did you know that it only takes a few minutes of direct sunlight a WEEK to make enough vitamin D for your body? Did you know that even though your milk has a lower amount of Vitamin D, its 100% absorbed by your baby? Formula has to have absurd amounts of Vit D because a baby can only absorb about 5% of it because its in an unnatural state. Getting Vit D in its natural state is absorbed 100%, and coming from your milk to your baby, he's getting all he needs.
I breastfed both my boys, both through the winter in MN, and never gave either the baby vitamins (made by formula companies... which is why they are forced upon breastfeeding moms, they want your money one way or another), and they never ate rice cereal either.
Your baby is telling you something, his body doesn't need these unnatural things. Expose him to sunlight when its out, a few minutes is all it takes. Even if its once a week, expose his face, arm, whatever, to direct sunlight for 5mins. thats it. Even through a window works. Get some sunlight yourself, and your body will add the right amount for your baby into your milk and it will be 100% absorbed by your baby, just like nature intended.