The concours correct and properly working starter solenoid that you seek can be purchased from Macs Auto Parts or Dearborn Classics, as they are the same company. Not only does it have the correct C7AF-11450-A1 number stamped on it, but it also has the correct vent. The only thing it doesn’t have is the paint dab, which you can add yourself. The cost is $42.79 and it is listed as Part #: 44-40314-1. I have personally had the one made by AMK and experienced the same problem as everyone else, then I purchased this one from Macs and I have had no problems.
JayCat