Wooden Vent Cover

We have wooden vents in our house, which do not have louvers so cannot be closed off. We had an air conditioner installed, and wanted to close most of the vents on the main floor in order to direct more of the cold air to the upstairs. I designed a vent cover to clip onto the bottom of the vent. This way it keeps the clean lines of the nice wooden vents, while at the same time forcing more of the air to the upstairs...