We looked for replacements for our 2008 Winnie and there were none available any longer from any vendor I contacted (including the one that CloudDriver linked.)
Similar to what beetlebug78 said, we had ours done by a body shop when we had them re-do our sealants last year. We needed just the front and back done. Not exact, but we're happy. Actually they changed the lettering for the Winnebago name to the flying W lettering and we like it better than the thinner font that was stock.
You can see some pics on our blog:
http://winnieadventures.blogspot.com/2014/08/new-sealant-and-graphics.html?m=0