Not a viable item to stock in any c/van spares shop not enough call for it plus too many different kinds/patterns.
You could contact a local c/van repair shop and ask their advice.
What's on there is a vinyl so you could use a vinyl wall paper from the DIY stores using heavy duty paste. You MUST strip off the existing vinyl or the new won't stay stuck for long. Don't try lining the wall to save striping it either as you end up with the same results, it will lift off at the slightest damp period.
If penatrating damp caused this problem then check all trims outside around the damaged area and on the roof, the trims may need additional sealing using a clear sealer like I do. Clean the area to be re-sealed put a bead down the edges of the trims and run a wet finger down the bead of sealant. Tip on using the sealant DON'T cut the end of the outlet tube leave it as it is and build up layers of sealant if necessary. Cutting the outlet tube make too much come out in one go and makes a hell of a mess plus wastes a lot.
Hope the price you paid was right!.
Nobby
June 2008