We use a very flexible, interlocking tile mat, purchased from Dri Dek. https://www.dri-dek.com
Ours is 3' X 5', and of course, it can be made in any size. We used the 3 X 5 with our 16' Bambi, and are still using it many years later with our 19' Bambi.
Ours rolls up into about a 6" diameter by 36" roll, and I stick it in an old collapsible chair bag. We've always stored ours in the garage, and throw it in the back of the pick-up for trips, but it should fit in your rear outside storage bin.
You'll have tabs on two sides for attaching more tiles, but I cut mine off for a cleaner look. Water runs right through it, and very easy to hose off when it gets muddy.
I've attached an image, but the mat is not real easy to see. It's a clean design, so blends well with an Airstream.