If your bellows is actual leather, Lexol works well, although it is somewhat expensive. I've used standard metal polishes on metal parts before with good results (brass cleaner on brass, chrome polish on chrome, etc..) Keep it dusted off and free from grime and dirt and it should last a good long time.
as an alternative, I have a B&J 8x10 Commercial I refinished in satin black lacquer, all of the "chrome" bits were nasty, a quick scrub with a scotchbrite pad brought out a lovely brass finish, a quick polish and lacquer and the camera looks lovely. BTW, the chrome is usually just polished nickel, comes off fairly easily.