All weather mats when the back seats are folded down

Hi All.

New Prius owner. Just got a 2010 Prius. My wife and I are loving it. However, it did not come with any floor mats, not even the carpet ones. We are pretty active outdoors so we will be getting the All Weather Mats soon. Prob going to go with Weathertech since the OEM ones do not look like they cover very high under the gas/break pedals. We will get a cargo area mat as well too.

So my main question is... does anyone know (aside from DIY) if anyone has a mat that can go on the back of the back seats when the seats are folded down? I'm very much an ocean person. I surf every week, along with dive and fish. I'd love to have some rubber mats to protect the back of my back seats when they are folded down.... even possibly have them "connect" to the rear cargo mat so it can protect the back even more from spillage.

Any thoughts?

THanks!