The Home Depot has a hot deal on Honeywell Allergen Plus Filter 4 Packs. They are normally priced at $42 – $44.99, but are just $22.99 today!! That makes them just $5.47 a filter!!!
There are many sizes still available, so you will (hopefully) find the one that you need. I would hurry though as the last time they had this sale, they sold out very quickly!