I believe there are places that can remake a VIN sticker (such as if the trailer was in an accident and that sidewall had to be replaced), but I've never researched them. Chances are it would look a little different than original, but would contain the same info.
As John said, a lot of times the clear film over top is what fades. If you can scrape that off with a fingernail, you might reveal the original sticker info. It seems that most Sunline VIN stickers got a clear film, just some weren't very thick or good.
I think you could check with your local police department- ask for a VIN check and once they verify, ask them where they recommend you could get a new sticker from.
If you need the info for a VIN sticker, like tire specs, weights, and build date, let us know.