Date: 10/14/2008 8:18 pm EDT
"Flange Extensions" do exist and are available at the Home Centers.
Alternatively extra tall wax seals (rings) are also available. Use the wax seal that has the funnel made into it.
It is also possible to stack two wax seals for additional height. One with the funnel and the second without the funnel.
Don't forget longer flange bolts will also likely be required.