Could you try a sippy cup/straw cup? I’m in the same boat, going back to work and she has very little formula, nursery helped get my little one with the bottle too, so hoping it works this time round too
Try mixing the formula and breast milk to slowly introduce?
Have you tried watering down a bit more than the recommended amount? It won’t hurt them as they drink water anyway. We put an extra 1 Oz of water in as breast milk is much thinner than formula. Also my BF baby will only have cow and gate - we tried them all but she just prefers it.
Are you giving it warm? But also stick with it. It may take a while for him to get used to it. How long did you try each brand before moving to a new one?