I found this one on amazon, but the active ingredients are different. Mine has sodium alginate, sodium hydrogen carbonate, and calcium carbonate. I would think it's less effective without the sodium alginate since it's not just another antacid. Maybe they just don't sell the same product in the US....

https://www.amazon.com/Gaviscon-Strength-Antacid-Fast-Acting-Heartburn/dp/B000GCLEE8/