Steak and potatoes.

You need to check out some crunchy ultra lib child care sites. Of course they will say there IS no substitute for mother's milk, but after that you'll also find home made formula recipes and other ideas to keep the lil' gals drink down.

Also- look up subjects like acid reflux, lactose/soy intolerance in infants.

BTW: Are there no local parents groups nearby? In any I know of there are always 10-20% of parents that have reflux issues with their kid(s), and they all trade solutions and war stories. Online is OK, but can be slow and often contradictory. Nothing like real-time with someone face to face. Good luck!