I picked up a couple 50 gallon upright containers at a feed store in downtown Florence. Right off Veteran's drive and I want to say Cherry st. It's only a block or two off the main road coming over the bridge after taking a right only Veterans. That is if you ever get out that way. They were used olive shipping containers with a large sized sealed screw on top. You may be able to find something similar locally. But I just mention them because one of the drawbacks about the drums is the small openings. Can't easily get a ph/pump inside them. These you could climb inside since they're shaped like a big jar. The cap is only a few inches smaller in diameter than the barrel. Their only drawback is they need to be cleaned before use. Mainly for the smell. But they're nearly 1/4" thick rigid plastic. Very sturdy, $16 there iirc.
Now that I think about it. This was 2 years ago, so you may want to get someone in the Florence area to drive by and see if they even have any anymore before making a trip. I would but I'm currently living in Memphis and won't be back there for several weeks. They kept them just outside the front door in a large outdoor style dog kennel.
HTH,
Will