You haven't looked very hard.
First off, you don't want to remap the controls in pinmame, you want to remap the controls in visual pinball. So fire it up, go into the settings and remap away.
Now by the odd chance you ARE wishing to remap the few keys that visual pinball doesn't control (the joystick for baby pacman is the only thing that comes to mind) you simply click on the dmd display in-game, use tab to get to the menu (just like you would in mame) and remap the offending keys (again just like in mame.)