Hi Steve,
Sorry for the late reply. I ended up making friends with a Parts employee at a local Acura dealership, and he gave me an HDPE2 drum for free (its only prior use was to hold tire/body cleaning soap; the employee told me that it's the brand they use to pump through the car washing machinery). It's kind of soapy/grimy, but I will probably cut the top off and pressure wash it.
Since like dissolves like, though, I may have to find a different material to get rid of any remaining soap residues after the initial washing.