Google Portazone to find one, or Google UV ozonators. I don't recommend UV because the lamps contain mercury which potentially ends up in landfills (as if we need more mercury in our environment)The lamps also have a short life span and the ozone output drops off significantly after 100 hours of use. I still recommend corona discharge for ozone-in-air applications. In most cases the amount of NOX produced is far outweighed by the benefits of the ozone produced. Some people have a rather bad reaction though to the small amount of NOX.
Hope this helps