http://www.mcloone.com/products/nameplates.asp
Here's one example of what these companies can typically do. But just to let you know, I've looked into this type of thing (not for canoe nameplates) and find that whether it's a silkscreened t-shirt, something fabricated of metal, or anything that's not simply digitally printed, it's always prohibitively expensive.
I imagine that considering the setup charges for creating dies to stamp or cut the metal...
programming the logo and words into the software for the laser to cut...
or burning the screen for printing the color onto the metal plate...
would probably leave you with something silly, like a $1000 nameplate. That's assuming you can find a company willing to go to all that effort for a one-off, as companies doing this stuff consider 500 items a "short run".
Now, if you would be building your own canoes for sale, then 500 nameplates for your own small boatbuilding company is a lot more reasonable to consider! Good luck, and let us know.