The Home Depot, Lowe's and EcoFoil all sell magnetic ceiling air vent covers to fit a variety of different register types and sizes, as of 2015. The Home Depot and Lowe's both offer free shipping directly to a local brick-and-mortar store, and EcoFoil provides installation guides to simplify use.
The Home Depot offers flexible magnetic air vent covers that adhere directly to registers using magnetism, allowing them to work well upside down on ceilings. Shipping directly to consumers is free for orders costing more than $45, and the retailer provides user reviews so customers can read about others' experiences with the vent covers.
Lowe's offers a variety of air deflectors and vent covers for ceiling use, and some flexible models allow users to trim the shape to more accurately fit the register covered. Lowe's provides free in-store pickup for shoppers as well as free shipping to homes and businesses on orders totaling more than $49.
EcoFoil sells fixed-size magnetic air vent covers that are insulated to help provide savings on energy costs, and air vent covers that work on both magnetic steel and nonmagnetic aluminum vents are available from the company. EcoFoil offers shoppers a toll-free number for assistance with purchases, and many items are covered by a 20-year limited warranty.