you can't please put best answer next to this

I've found 3. I stole 2 off people, and I found 1 in a locker.

Opposite the Hair Dressers The Happy Mullet i think it is there is a building with ladders behind it. climb up and there should be a townie there. do his errand - (throwing water bombs at people passing by) and you unlock it. then u can get them by using sinks

hmoonman is right!