Or maybe a jeweler? There is a place at the mall that engraves stuff, I think it is a national chain, Things Remembered or something like that.
You have to go to an actual jeweler and one with a proper engraving machine. Most of the places like 'Things remembered' use laser engravers that can only be used on the products they sell that have a special coating on them for the laser. I had good luck with a one-off larger jeweler when having a Zippo engraved with a custom image.
You could also try a trophy shop, though they may only be equipped for text, and not be able to engrave images.
JGL