Here you go, this is the absolute closest I have found short of going to the autobody store.
Duplicolor HPW101 Wheel silver. It has a very fine metallic to it.
http://www.duplicolor.com/products/wheelCoating/
I bought it at Pep Boys, but probably available anywhere you can get car parts.
I painted both engines and exhaust, the only part that is still OEM silver is my water boxes and it is so damn close. I was very particular about the color, it has no effects from chemicals. After each wash I use almost a full can of Seadoo Lube on the engine bay, so that is sitting on there all the time, this also gets the color just that much closer to OEM. Going on it's 5 season I think now on the one engine and 4 season on the other.