Even if you are able to find the same pattern and color, it probably still will not match, as the wall paper in your camper has aged, faded, been exposed to camp fire smoke, cooking smoke, and water vapor. It's kind of like touching up the paint on a wall inside the house. After a couple years, no matter how hard you try, the new will always look out of place against the old.
If you don't mind this, then keep searching. But after searching and you finally find it, you may still be disappointed with the end results. It might be easier, better and more satisfying to repaper everything. Here's your chance to really beef-up your camper if you want.