Ian,
Douglas changed the kick-start quadrant to a coarser pitch tooth profile during EW production (starting with gearbox prefix RG/E); apparently they had trouble even back then. You can use either the early or late style, they interchange, but you naturally have to use the appropriate fine or coarse pinion to go with it. The quadrants can be made new by sawing portion out of a full gear. But the pinion has a special rounded tooth form to deter jamming, so you can not make them out of a standard gear.
If you order a new kick-start lever return spring from LDMCC spares, be sure to tell them what it is for, as there are two styles: a three-speed (what you want) and four-speed versions, which look quite similar.
Kick-start levers can be made easily from welded fabrications (lever + hub); the only difficult bit is you will need to make a punch tool to form the serrated taper in the hub. You will also need about twenty-five ton hydraulic press, and at that you need to heat the hub blank up cherry red to get nice, well defined serrations. Use hot work tool steel for the punch. I tried a four pound sledge first, but the press worked better. Make the hub oversized and machine afterwards (it will distort and swell quite a bit during pressing.)
Good luck!
-Doug