Acid can be found in: Abraxo Cleaner, Abraxo Cleaner Industrial Grade, Acid, Antifreeze bottle, Bag of fertilizer, coolant, cracked deathclaw egg, Ichor sac, makeshift battery, Suprethaw antifreeze, undamaged Abraxo cleaner.
Thank you a lot for sharing information that is readily available on the Fallout Wikia! I'm sorry for being nasty, but come on, this is a bit of a redundant thread, don't you think?