Any place that sells metal polish.
CTire, WalMart, NAPA, Princess Auto, etc.
Second on the Solvol AutoSol polish. Good stuff! $$ but worth every cent, and a little goes a long way.
In a real pinch, when very little material needs to be moved, grab a tube of regular (not gel) toothpaste. Very fine abrasive, sticks where it's put.
The CTire assortment of Dremel tools, includes some rouge in a tiny container. Still about enough to clean up a dozen or so actions. add a drop of oil, and mix it a bit, to make paste that can be stuck onto various parts.
Some of the CTires also stock larger blocks of it, with the grinding wheels.
Cheers
Trev