To add another word of caution. The covers differ depending on model and year, as does the inner cover and timing side crankcase half. Early covers only have two screws at the bottom, later have three, with an additional dimple added to the original casting profiles to take the extra thread. BSA Piled Arms logo is cast into the cover, from memory on the Star Twin to start with, A7 was plain. But of course over time you get what you get. These features are shown in Musky's pic.
That is an easy repair, but the casting would do in the short term with a cold epoxy repair while the search begins. From the picture my specsavers show the crack to be over the dynamo chain, which runs in grease, so any leak from here should be minimal anyway.
Swarfy.
Additional. Footrest fixing looks a codge. The proper footrests are plain tapers each side, with a special flanged retaining nut 67-4852 and stud 67-4029 into the frame forging. Left side have left hand threads, nut is 67-4856, stud is 67-4041
