Electra clutch query

Ian, have you tried the AJS & Matchless Owner Club as it was used in their lightweights too. Part No 22765 or 043342 I believe.

If you cannot find one, might it be possible to make one from two readily available plain plates?
One of the plates would need modifying before joining.  
If you get stuck, pm me. 

Ian, hope you can get the proper item for piece of mind. Suggest Norvil worth an enquiry. 
The additional shoulder on this special plate goes against the inner face of the clutch basket. The ears of the stepped plate should be just held off the bottom of the slots in outer of clutch basket. When engaged the full collection of plates including clutch basket are solidly squeezed together. 

If you go for a normal flat plate in place of the stepped plate, the flat plate tangs will rest on the bottom faces of the clutch basket grooves. Worth checking that everything sits flat and not held up in one or more grooves because of a burr, or unwanted radius in the corner of a groove. AMC were obviously aware that in this scenario the full plate pack is not solidly squeezed. The plain plate is supported only at the tangs, and could buckle inwards given time and friction heat. 

You might consider another alternative which has done me for many years and thousands of miles and shows no negatives yet. Put a double sided friction plate, with plenty of meat on it, against the clutch basket. Now a normal plain plate, then the normal 3 plain, 3 bonded, and the single side bonded. Don't worry that the inside surface of the clutch drum is not as smooth as a plain plate. The total pack is now thicker by about half a plate thickness. It all squeezes up solidly. All the plate tangs are on the unworn parts of the clutch inner/outer. You will need to find an extra friction plate. 

With my plates, which were all part worn, there was no chance of the last single side bonded plate leaving the basket groove when actuating the clutch. Good. And hopefully your clutch adjuster screw will still lock with the nut as before, but a bit nearer the top of the adjuster screw. Good. If you think a longer adjusting screw is needed, consider thinner pressure plate used on some Dommies, but be aware a longer screw, if adopted, must clear the chain case at full lift. 

Serves you right for asking for more thoughts. 

Peter