Jan,
I got Heather's first bag at the local pharmacy. Just tell them you want a bag for gravity flow feeding, not to be hooked up to a pump. The pump bags have the little cassette that goes in the pump. The gravity bags are basically the same, just without the cassette.
Hospital supply companies also have them. Just check the yellow pages. You should also check to see if they are covered under your insurance plan. Good luck.
Rainbows & hugs,
Rosie