If I had to bring one thing for acid reflux, it'd be a bottle of citric acid powder.
Hopefully this doesn't come off as crackpot-ish, but it's solved the bulk of my acid reflux problem.
Any evening I ate pizza or legumes, like clockwork I'd be lying awake half the night from extreme acid reflux, the kind you have to swallow. If I wanted to get up early, then I couldn't eat my favorite meals. It was terrible. Antacids seemed to do nothing (i.e. stomach seemed to compensate with more acid).
Dad always drank soda (carbonic acid) with his meat to help digestion, and I wondered if there was anything to this. Some websites say there is. The theory is that acid reflux is a result of excessive stomach churning from indigestion, and that supplementing your HCl with some extra acid can actually aid digestion and calm the stomach contractions that are pushing acid up your throat. So I started drinking dilute lemon juice with the acid-causing meals. It turns out I can actually sleep at night after a problem-meal. So I drink lemon juice with almost all my meals now.
Could the effect be psychological/placebic? Could be.
Will it work for everyone? Maybe not.
But the acid I still get with any meal now is manageable/ignorable.
So, PERSONALLY, on a trek I'd bring a bottle of citric acid powder.