I'm OK for most of the groceries. I had a couple of these
GSC Technologies 11 in. x 13 in. x 13 in. Black Milk Crate-MC131311-002 - The Home Depot that I moved from the Subaru to the MY when I got it. They are zip-tied together. It's the milk and juice bottles. I don't bag them as I think they are too heavy for my reusable bags and I won't use the single-use plastic. I can't get a milk bottle in the space along with a grocery bag .
That Tesmanian one might work better. Do you have it? Does it stay put? The milk crates slide all over the Tesmanian mat I have back there.
Those pocket extenders might help. I think I'd rather have a lid there but might try those extenders if I can't find anything else. If they hold decently, they should keep stuff from falling in which is my mail complaint.