As one of its daily deals, Home Depot takes up to 40% off a selection of vacuums and floorcare tools, with prices from $6.98. Shipping starts at $5.99, or get free shipping on most orders of $45 or more. (In-store pickup is also available.) Some best bets, both with free shipping:
Hoover via eBay offers the Hoover 2x CleanPlus 64-oz. Carpet Cleaner and Deodorizer 4-Pack for $35 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.