The diagram you posted for the non battery model has 4 pins, there are only 2 wires to the regulator and what looks like 2 wires to the outputs of which one is the horn. For what it costs, its got to be worth getting it , connecting the 2 wires to the regulator as per diagram and then measuring the DC output using your meter as per diagram. If you get around 10VDC solid through the rev range , then jobs a good un.. you just then need to adjust the resistor to get the correct readings on the gauge- OR take a road trip to Derbyshire England and i do it myself....
The link you posted is for a regulator/rectifier. Do you mean I should somehow hook it up as per the diagram to the current 3 pole regulator, or just replace the 3 pole with this 4 pole?
In which case the hot wire incoming from the stator would connect to either G, and the wire going to the circuit (and gauge) to the A, correct? I might actually be able to borrow a similar regulator from a different scooter to try it out.