I am in correspondence with an Australian Scott owner who says he has a Miller distributor on his post-war Scott. He needs a new rotor arm. Does anyone know where this can be purchased? I have done the rounds of vintage electrical suppliers with no luck.
New Miller rotor arms AND DISTRIBUTOR CAPS are available from Kip Motor Company in Dallas Texas. I got them made for my Dragonfly some years ago and they are a superb copy but because they use modern resins rather than Bakerlite so they are slightly heavier. I have tried on many occasions to get the Douglas spares scheme and the Scott one to jointly buy a few because they are very expensive but there are significant discounts for quantities.
Their website is https://www.kipmotor.com/catalogs.htm They do not show the rotor arm in their catalogue but they do have them. Their response to emails is very slow so better to phone.
If no joy in sourcing Miller bits consider changing to a Lucas DKX2A distributor, as also used on late Shipley and early Brum Scotts. They are MUCH easier to get parts for as they were also used on Sunbeam S7 and S8, early 500cc vertical twin Royal Enfields, etc.. A lot of pre-war cars also used the same centrifugal advance distributor, but with four-cylinder type cap. As a consequence there is a healthy supply of parts.