I make signs, I make signs!!!
Unfortunetly I live in Australia at the moment so I probably can't help much, look for engraving shops in the phonebooks, mostly engraving is done via CNC machines so you can give digital designs and they'll engrave it for you. There's plenty of metal choices, and ask for a resin based paint for longevity (the paint's not yours). Vinyl is also a very good choice, but be aware that if you want some really small kanji they won't come out properly.
Etching (acid or otherwise) is done to very shallow level so it is easy to scratch the paint off (again, I recommend actual engraving over all of this but usually that ends up as being more expensive)
Wish I could help more, but again, Australia...
-Amir Barak
"You get what you pay for, But I had no intention of living this way" - Adam Duritz