Hi @mayblin. I got my generic Altelvia from my Publix pharmacy. I know that my local Walgreens carries it, too.
Check out GoodRx for your local pharmacies that carry generic or brand-name Altevia and GoodRx discounted prices at each local pharmacy. GoodRx is very useful for buying meds, especially if you don't have a good drug plan.
Drugs-com is useful for drug information, including what companies make the generic, although I'm not sure that information is always current. But a call to the generic company can easily confirm whether they actually make the drug.