Depending on what you want to watch.... try WHDload with tool type NTSC it will switch to 60hz and eliminate some flicker. Side effect is part of the screen may be not visible if the game / demo didn't have borders and music may play back faster. Not perfect but it is free.
Also the AMBER has a pot (little screw by the VGA) you can use to tune flicker. Don't adjust it too far and mark where it was in case you make it worse