Hoover via eBay offers the Hoover 2x CleanPlus 64-oz. Carpet Cleaner and Deodorizer 4-Pack
with free shipping
. That's the lowest total price we could find by $26 for this quantity elsewhere. (For further comparison, we saw a single bottle for $10 last month.) It works with most carpet cleaning machines and is biodegradable and nontoxic.