I've never seen one for either...Just the full regulator (inc motor) or just the motor. FCPEuro has the reg (Volvo) for 340.. and AutoZone has the motor for 160.
The front is entirely different than the rear, and I've never looked at a rear other than a diagram. I repaired my front with a guide I found online with the metal wheel from a sliding glass door.
I know LloydDobber has replaced his rear, there may already be a post about how, for info on how to do it...
Sorry I'm not more help, best of luck.