I think a workshop might be easier to get a free timing belt Norm as they just throw them out.
The timing belt most probably will need the width narrowed as the wider width has a greater surface area and the force per square millimeter can be lower, which might suggest less grip .It would be narrowed to fit the rover drive anyway.
The problem might be if this doesn't work it's going to waste time.
I did see a Nissan RB30 cam gear and belt is about 125 mm width,
