Walmart offers the Black & Decker Table Top HEPA Fresh Air Cleaner, model no. BXAP041, for $19.99. (Amazon charges the same with Prime members.) Choose in-store pickup to avoid the $5.97 shipping fee. That's tied with our mention from two weeks ago as the lowest price we've seen. (It's the best deal now by $7.) It features three speeds and is suited for small- to medium-sized rooms.