PLEASE HELP of you have any advice on this matter im a FTM

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Okay My best friend is coming to the US for the first time, One of the things we're going to do is visit the zoo with him and my family. It will be an all day thing (there is likely to be other all day outings as well) My baby has never and will not latch. I've been working very hard to get my supply back up! What should I do?? I do have a small manual pump I guess I can take that but it takes me 30+ minutes sometimes up to an hour to express my breast "empty" with an electric. Should I just make due with that, will it hurt my supply terribly? I know it will be uncomfortable as hell if I don't pump