I ordered 6 5gal and 2 2.5gal Scepter water cans from BQM a couple years ago. Cost+shipping was indeed retarded, but these cans are pretty awesome, and they lash into the DEI 1606 frame perfectly! I really liked them in the service, they are pretty hard to break. These cover our 5-person family's emergency water supply for 7 days, and are pretty easy to transport.

Stig, wipe out what you can, then try sanitizing them with a strong bleach mixture. I'd bet it's some kind of slimey mold from being closed up damp and warm. When empty, you need to store them open so they dry out, but I pretty much just keep them full.