Where can I buy a 4'x8' container with a lid?
Using the 4X8 flood and drain trays only gives you about 7" to work with as far as depth. You'll want at least 12"' for the root mass to develop properly in Aero. Our first test was a flood and drain tray and the root mass went straight to the bottom and bunched up. The plants grew fine, but there was no advantage over just using flood and drain.
Nobody makes a 4X8X1 tray with a lid. We looked. The problem is the 4X8 flood and drain trays that most Hydroponic companies make are actually 4X4 trays that are plastic welded together. Most of these trays are made through a manufacturing process known as Thermoforming. A sheet of ABS plastic is heated up and then vaccum formed over a mold. The reason larger trays are not made this way is because they would be flimsy and would crack easily.
The only way to make a 4X8 tray large enough for Aero is through rotational molding which costs a bit more to tool up for and manufacture. However, with rotational molding, you can make the trays out of HDPE, which is non-stick and FDA approved. ABS plastic is not FDA approved, it leeches and will form build up that is difficult to clean.
I invested money into having tooling made to create large 4X8 trays for Aeroponics. We haven't started manufacturing them for sale yet, but will in the near future. If there was enough interest for a group buy, I could do a run for folks.