Just call the church office. There shouldn't be any charge. It would be a kind thing to leave a donation
Actually as a monsignor told me when I was an altar boy you can bless water yourself you take distilled water and bless it in the name of the father the son and the holy ghost and make the sign of cross over the container, thus making it holy water
I suggest you go to church on Sunday and speak with the priest about it afterwards.
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