Vredestein list the Quatrac 5 on their website in sizes (amongst many others):
195/50R15 82H and 195/50R15 82V
This size could be matched to front 175/55R15 77T tires.
175/55R15 front matched to 195/50R15 rear could be considered a standard upgrade for the 155/60R15 front and 175/55R15 rear sizes.
This is EXACTLY what I was looking for in the rear. However, I found these tires on Tirerack, and since the website did not show 195/50/r15, I falsely assumed that Vredestein did not make this size.
Just found them (and ordered) on Vulcan Tire. So I guess now the only concern is the difference in speed rating... Since front tires are Ts, I purchased the H version for the back. This way the front and rear will be only one level apart. as opposed to two with the Vs. Will report as soon as the tires are installed.