If you can’t find one anywhere, then you can just use any plastic bottle with a spout that squirts, like a
Rubbermaid picnic bottle or a
kitchen squeeze bottle.
The best, once again, is a
small travel squeeze bottle, which is listed as a 4 oz. bottle, but actually holds about 5 oz. or about 140 milliliters. Fill it up from the gallon of saline solution. Keep the small bottle in your shower, but store the gallon bottle somewhere else.