If you run out of Holy Water here’s a list of priests that will bless your water supply. Additionally, you can call on them for backup if you find yourself in a difficult situation.
In addition, a blessed rosary will work in a pinch. Stick the rosary in your bottle of Holy Water and the rosary will cleanse the water and purify it, making it usable against all demons. .
Standard Rosary
The Demon Conspiracy 