I'm sure you would sell a small batch of sprockets as there are many James ML owners.......
Apart from the engine, gearbox and carburetter parts (Villiers), plus the proprietry parts (Lucas lighting) there is no source of original new old stock parts for the ML....everything has to be sourced second-hand or from the very few sources making replica parts (Metal Magic for example).....
The wheel hubs for the ML were made by The British Hub Company in Birmingham laced to Dunlop rims......the BHC supplied wheel hubs, brake plates, sprockets, etc, to many of the smaller manufacturers including James. Although it's often been stated that the wheel hubs are unique to the ML, in fact they are BHC generic items with largely the brake plates and sprockets being supplied to particular manufacturers specifications.....so you can still find sprockets occasionally that will fit the ML along with the correct number of teeth, but they will always be few and far between....
I do know that post-WW2, the UK accessories company MCE manufactured an aftermarket replacement sprocket for the ML........this component is marked with the MCE logo, has 42 teeth and fits.....the only difference between this and the original part is the MCE item has a series of large circular holes around the part rather than the "oval" holes of the original.......