A workaround :
By having an alternative keyboard layout and then by ticking the scroll-lock box within (for gnome) :
System > Preferences > Keyboard > Layouts > Layout Options > Use keyboard LED to show alternative layout
The backlight LED's on my system will also come on when any alternative layout is selected..
This method is helped by the fact that the Layout Options will allow duplication of any one layout as alternative layouts.
N.B. Probably due to the nature of scroll-lock, system navigation will often cause switching between the alternative layout and the default layout,
so assigning a hot-key (again found in Layout Options) for switching layouts is worthwhile here.