Looking for big containers for aeroponics unit.....

In my past grows I have used fence posts with 9 plants on each fence post. I think I want to do something different with my new garden.

I want to use one large container to grow at least 20-22 plants per harvest.

This would mean a container roughly 7-8ft long by 4 ft wide.

Does anyone know where to find large containers? They do not need to be too deep, a couple feet would be great. I don't need nothing fancy either.

I would be expanding this, and will eventually need multiple containers.

Fence post work pretty good, but making the resevoir and grow area the same container appeals to me.

Thank you.

4 of the biggest tote tool chest at a local hardware.

other than that; custom made with black pond rubber. PT frame; foam silver insulation sheets; foil tape; done.