It would help to know what year and model outboard you're looking for, but I found replacement decals for my Evinrude SkiTwin on eBay. There are tons of listings for different models, just do a search for "Evinrude decals" and a bunch come up.
as mentioned above, year and model will help.
or, look through the thousands of examples
that this guy has in his ebay store.
-or- stop by your local sign sticker shop and see what they can do for you.
if you don't want to pay $60-70 for replicas on Ebay there is a seller, fatmans_stickes that has some more generic brand stickers and he will do requests too..
I painted my old 9.9 bucket in olive drab green added some camo merc stickers. not perfect but much nicer than the house numbers the previous owner had stuck all over it lol.