Amazon offers Prime members the Lavish Home Mosquito Repelling Net Canopy for Beds, Hammocks, and Cribs for $8.82 with free shipping. (5StarDeal via eBay charges about the same.) That's the lowest price we could find by $2. It measures about 12 x 8 feet.

Update: The price has increased at Amazon; however, 5StarDeal via eBay still offers it for $8.99 with free shipping.