I had a 54501A a long time ago, gave it to a friend. When I took it apart, it looked like the internal monitor was a Japanese-sourced unit (possibly Panasonic from memory). It is very likely the signals to this monitor are just something like VGA, so it is probably possible to do so, but you would need to find an LCD panel that fit, some way to get the right supply voltage to it, and fit it into the case.