I've been looking to do this myself. As far as I know, the 10th gen Corolla XRS, 2nd gen Matrix that have rear discs and torsion beam rear suspension, and possibly the 11th gen Corolla S all have rear discs that we can install onto our 10th gens to replace the rear drums. There's a DIY on ToyotaNation for the XRS swap but not for the other two however they should be similar.