I have an heat/air vent that comes into the kitchen below the sink. The dimensions are 12" x 3". There is very little space (width wise) for a vent cover as it would butt up against the bottom of the sink cabinetry. I do have space along the length. I am in need of a VENT COVER as it was missing when we bought the house. To date, I have been unable to find a vent cover that will fit the dimensions 3" x 12". Please advise me what to do.