We have and use 2 large drying mats at home and really like them.
On our current trip we found the perfect size for our counter extension. It was $8.00 at a local backpacking store.
My wife modified it by sewing 2 small pieces of Velcro so that it doesn't blow off the screened side of the door handle when drying or fall off while in transit.
It's not as thick as our mats at home, but is perfect for camping.
Like ours at home it is washable.
Here are a few shots as well as a screenshot of a CW link that I found in a quick search -
