Double chest of glass bottles with a hopper going into a dispenser facing a source block
Another hopper to collect filled bottles leading into a dispenser facing a cauldron, with another dispenser filled with buckets to collect water once it's full, and a couple hoppers to collect filled buckets and empty bottles. Empty bottles are then circulated back up to the double chest and the cycle continues until it runs out of buckets
Connect it to an iron farm and an auto crafter to avoid needing to refill buckets, just make sure you have enough storage space