The is a huge military surplus store/yard NW of Ogden, Utah that would have what you are looking for but I can't remember the name of it. The WWII tanks would be a bit small for what you are are wanting. What would work great would be what is referred to the Supersonic 600 gal Centerline tank (source of Centerline's handle?) for the F4. The standard tank is much more flimsy but would work as well and there should be thousands of those out there if they have not been recycled.
I'll try to locate contact info for the Ogden site.