Transitioning from ebf to bottle

my babies been breast feed  since birth and at 5months we introduced small amounts of pureeed  vegetables.

I want to start to introduce bottle ready for when I go back to work,

 i have  tried him on hole organic however whenever Ive tried He pulls a gagging face like he hates the taste. 

He has no problem with bottles as I have expressed before and he has taken bottle fine. 

Can anyone suggest a better tasting formula? Or advice on if this is normal and to continue on? So far I've given up due to him resisting and ended up breast feeding 

thanks In advanced