So what is you want. A cadet Safety lever (Martini Cadets don't have safety's) or is it a Greener safety lever. Can you provide a picture of the gun and action.

Is this the type safety lever that attaches to the safety spindle with a screw or the type lever that has the spindle integral with the lever and and is held in by a keeper half screw the screws into the action and turns into a slot in the end of the spindle?

This is a good place to start looking, but a better place to look is the Yard Forum on British Militaria Forum.