Who's stuck a rear defogger in their A-body?

Think of making my car abit more user friendly during winter. A rear defroster sure would help sometimes in this foggey place I live.
I have a few questions though.
Firstly the only dart rear windows I've seen with factory defogger elements, have been damn pricey, but has anyone put a rear window from say a mid 70's dart in to a late 60's dart?
Another option is the aftermarket stick on defoggers, are there any good ones that look factory?
The other option is the defogger blowers, that go in the rear speaker hole. Do they work? Do they heat the air? Or is it just a blower? I've never seen one in person.
Hope someone can shed some light on the topic.