A warm welcome , old vet , have a look in the section Services ,parts ,manu etc, and look at Priory Mags Ltd , Beezamac is also a very helpful and knowledgeable member , if he doesn't know the answer to your question then I'd give up !
By the way why not add a little "meat to the bones " re yourself and your etc in the bikes pictures and members section , you'll find everyone friendly and helpful ,enjoy the forum and your BSA ,Bob