If it is internal condensation you should be able to repair it, look on you tube for several videos on this. If it cannot be repaired you can get replacements made to order but they are expensive, try EECO and caravan crazy but I would try dismantlers first.
SCM are possibly he biggest but if you google caravan breakers there are several others. The window should fit all the Avante range for that year, as it is common to all of them and probably other years when that model run was made. Like cars they do have model runs for several years with minor updates. If it is for another year though make sure you have the measurements to check it.