does anyone use bottle liners? I did for my second and plan to use for my third. works great because…

does anyone use bottle liners? I did for my second and plan to use for my third. works great because easy clean up but also u can get all the air out which really elimates gassiness and stuff. but any who... if any one does have you found a way to buy by cases? I have looked and looked and can't find anywhere to buy by cases.