Hatchbag. I bought one back in 2008 for my Ford C-Max. I had them custom make it to my spec as the ones on their website only showed two versions: rear seats up, or rear seats folded, whereas on my car I’d completely removed all three seats.
Since that car I’ve used it in the second C-Max, Skoda Octavia, a Peugeot estate & am currently using it in my current Astra estate. OK, it’s not an exact fit but it’s not far off, & with 15 years use & abuse, (throwing a muddy mtb in, tip runs etc etc) it’s wearing well with no rips or tears. I specified it with the extra bumper protection flap, protects the paintwork on the rear bumper. Cost? IIRC it was around £110 at the time.
Money well spent IMHO.
EDIT: Sometimes Hatchbag advertise for people who have cars that they don’t currently list a product for to contact them & they’ll use your car as a pattern to manufacture a boot liner for. They then supply you one FOC.