Looking to replace six exterior bathroom exhaust vents on our house. They have weathered and are no longer white. They have all yellowed in less than two years. Checked with our builder, plumber and siding company with no positive results. Looking for suggestions of a company to replace the yellowed exhaust vents with new white ones that will not yellow. Can be hood or louver type vents. Approx. size of the exhaust vent hood is 10x10. Thank you!