Amelia is completely devoid of any battery carrying facilities. She should have the big Lucas GU11E battery that appeared in 1951.
Thanks to Brenton Roy & Guy Rayner of the AOMCC for these images of what I need to make, find, swap or a combination of the three:
Underside, showing the screws that clamp it to the primary cases.
Here is the strap, best English chrome plate, available from Acme Stainless in a rather more appropriate material.
And here is the large battery carrier, in position on Guy's 4G. As he says, his bike should have the small battery. Alas I don't have one to swap...
As a postscript to this request, the ever helpful Brenton sent me this: