If you want a super-cheap solution, just snag a furnace air filter at Home Depot or the like, then cut it up into shapes that will cover your intake holes. Another thread mentioned attaching velcro around the sides of the vent, and the air filter will stick to this. A few months ago I bought a $2 air filter at HD and chopped it up into around 15 one-use air filters. They work great! I still switched to the metal mesh filters at 2cooltek, but I may actually switch back to the air filter... go figure 😀