UL antacids?

What about pepto bismol repackaged?

Sorry to be a paranoid cardiac nurse here, but I hope you really are experiencing indigestion on the trail and not angina. Cardiac pain very often mimics indigestion and/or abdominal pain.

There are travel sized packs of Tums available.  Pills are small, rolls are about 5 cm x 1cm. Easy to carry. Or, flick out how ever many you want, and carry them in a small pill pockets Ziploc, available in pharmacies. Might wrap in foil first.

Baking soda? I don’t typically get heart burn, but I see 1/2 teaspoon is the recommended does, so it seems that could go a long way. And you can use it as toothpaste or to relieve bug bites, too, so it’s a multiuse item

Try to bring this up with your doctor and track down WHY this is happening vs trying to find a drug to mitigate it…

I had pretty sever indigestion and reflux issues and spent a month paying attention to what I ate and it just went away.

Basically I was drinking too much soda water and it was weakening my esophagus…

This can be a sign of something serious so just keep up with it… way easier to cure something when you catch it early.

Yeah, baking soda would be more compact than the Tums / Rolaids.
You could multipurpose baking-soda toothpaste by swallowing it after brushing your teeth!  Better yet, brush with baking soda and swallow that.

Or learn some geology, and find stream-rounded limestone or marble pebbles.  Swallow those.  No added pack weight!  There’s a decent vein of limestone in most of the Sierra around 2,000-2,500 feet of elevation (corresponding to gold-rush-era towns).  And spotter occurrences around 9,000 feet in a few places.

Best to be answered by your PCP.