What is the typewriter you have received? Depending on the model, it may take a standard ("universal") spool that should be easily available. In any event, you can always get a new ribbon and spool it onto the existing spools, so do not throw them away. 

Office Depot sells the universal spool ribbons.  I always wind them into the old soools to eliminate mechanical issues.  Once they’re would a few times, tie a knot to prevent it from coming undone as the spool unwinds, or to trip the auto ribbon reverse.  Make sure the red side is on the bottom, and happy typing.