We couldn't find a bottle without plastic, so we made one.
We started with one question while we were out shopping for a baby bottle: what is this made of?
The labels said "BPA-free" and the glass bottles looked like the safe choice, yet almost every one held the nipple on with a plastic collar, and nobody could tell us what else was in it.
So we designed & made the bottle we were looking for, from borosilicate glass and one piece of food-grade silicone, and sent it off to an independent lab to certify.