I requirement to find a marine reservoir? I need to find a reservoir of a few gallons to use...

I need to find a reservoir of a few gallons to use in a project I am working on. It requests to have an inlet on the top as very well as the bottom and preferably be pretty light. Both inlets obligation to either hold a nipple attachment on them or be threaded so I can secure a nipple on.

Does anyone know of a type of container that fits these specs?
I am going to put up crown molding,...
Answers:    depending on what properties the container needs to posess (clarity, strength, composition, flexibility, porosity, durability)... I don`t know a solar shower may work...???
I made a tshirt and want to outline...
you could always amalgamate http//www.freecycle.org in your aera and hope ones comes up or even put a post over to adjectives the other members and someone may enjoy one they are giving away