Have you thought about using a 55 gallon drum with a screw off lid? You could lay it down flat on some type of V platform. You can then run a
pump line and a return line running out from the top side of the drum using the attachments like I'm using with my cooler. If you needed to add water or
nutrients you could do so using the return line. The red drums usually sells for around 25 - $35 used. Here's a picture of the type I'm talking about.