I need a 3 X 10 Inches Ceiling AC Vent?

[airdogspace2]

The question pretty much says it all. Had a wall taken out in my basement. The Contract used the existing AC vent which was 3 1/4 X 10 Inches (from what I can tell). Before it was in the wall, not its in the ceiling. This vent size seems to be normal, but I can't find a Vent Cover for this size.
all I can find is 4 X 10 for the ceiling. I do find some 3 X 12 or something but thats for a floor vent?

Any idea where I can find a 3 X 10 Ceiling AC vent?