You could drill through the rear window and put the rear wiper engine through that hole ... with a high risk of destryoing the window.
But why would you need a rear wiper?
You are just not driving fast enughBecause rain gets built up on it and you can't see anything out of it when its raining.
OP, what you can do is put alot of rainex on the rear window. That way water will just glide off. It's not as good as a rear wiper, but it worked for me.