Problem Solved. - and the eclectic mix of my boat increased.
Reg / Rectifier off a Honda 50 on it's way!
And in case this thread is found by Landrover owners on google in 5 year's time, I found the link(s) and yes, kits to convert the 1950s Lucas electromechanical device into solid state do exist, although Triumph & Moggie owners seem to prefer them as they fit inside the old casing & keep it looking original. The landy ownwers seem to prefer function over form!
There are also lots of lower power ones for classic motorbikes.