Amazon.com: PreVent-It Soffit Vents 4 Inch - Only Design that Prevents Moist Air from Re-entering Home, Under Eave Exterior Vents for Bathroom Exhaust Fan, Screws Included, 4-Pack : Tools & Home Improvement
PartsExtra ABS Air Vent, Adjustable Round Exhaust Louver Grille Air Ventilation Cover Duct Fan Outlet Vent Soffit Air Vent for House Bathroom Kitchen Ventilation (6inch) - Amazon.com
Panasonic EZ Soffit Polypropylene Exhaust Vent in the Bathroom Fan Parts department at Lowes.com
Imperial 3 In. or 4 In. Eave & Soffit Vent - Gillman Home Center