I recently purchased a 40 year old home which has 24 inch baseboard HVAC diffusers/registers. They are triangle-shaped, with the back mounting to the wall, base to the floor, and slanted front containing the vent and output adjustment. I would replace them with the 18 inch registers I found at Home Depot, put my wood flooring is cut to fit the 24 inch ones, so I'd really like to use those. The problem is that I can't find any! Do you have any suggestions of HVAC parts distributors that sell diffusers/registers in this size?