Thanks Gregg, confirms my memories, and the Lucas bible agrees 100%.
I was going to suggest something like this one on UK fleabay - although you have no idea if its just been beadblasted.
That blue spark looks hopeful - it says it needs a rebuild. There are any number of ones there you could use as a core.
You will have to remove those 2 pegs underneath.https://www.ebay.co.uk/itm/Lucas-MO1L-Magneto-Ariel-Bsa-Panther-Norton-Blue-Spark/153888687754
I bought a similar magdyno & generator a while back. It wasn't strictly the correct numbers one, but as long as it spins anticlock and has provision underneath for the 4 countersunk screws, it should be good to go.
By the time you purchase something and ship it, you may as well have just shipped your existing one ??
I'd also comment that few bikes really NEED a functioning generator, I've noticed that a total loss battery system is perfectly good, unless you intend to really do a lot of night riding ?