Welcome to CruzeTalk. If the rear seats will lie flat someone will eventually make what you're looking for.
We have a CarId rep here on CruzeTalk. Post a question in their forum.Thanks for the replies and welcome, everyone!
As mentioned, the seats don't lie completely flat, so I wouldn't expect a rigid cargo liner but was thinking that there might be some sort of more flexible, roll-out option available. I found this...
They have one that is supposed to be fitted to the Cruze Hatch but don't show any pictures specifically of that vehicle. One image looks like it shows an SUV or van with a portion rolled out over the rear seating though... I'm going to give them a call later and see what they say about it. Will let everyone know what I find out.