gaviscon can be given to BF babies with out the need of expressing and giving bottles.....make it up with tiny amount of either water, or you can express a small amunt of milk for this, in a tiny sterile cup/pot and then syringe in with a sterile syringe, or a medicine spoon.
I had to do this for mine (3 had reflux and needed gaviscon and other meds), and it can work.
BUT and don't be surprised if this happens, it can make them sick it back up tho.
Sadly for mine (but then they were severe and losing weight, so a whole other minefield), they did have to go over onto the bottle. Having said that tho....they were also milk intolerant and as much as I avoided the triggers, something still got thro my breatmilk so they had to eventually go onto the bottle. That said tho, with my first refluxer(DD2), she was 7mths before that happened, then my next (DD3) was 9mths (altho she had other really strong meds for it from 4mths!!!!!)....it was DS2 who was on bottle for it really early....he was 2mths.
if tho you are able to get it in your baby with a syringe or spoon then fab and welldone.
It can work for some, and indeed does, sadly for me it wasn't to be.!!
HTH and good luck. reflux doesn't have to rule your life.....altho it does create a hell of a lot more washing