Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

This site may help and / or give some clues on No6 battery refit.
https://sites.google.com/site/johnengsdeadtechrescue/photos/john-s-ideas-to-restore-dead-technology/vintage-no-6-dry-cell-comes-to-life-again
You could use single D cell battery holders wiring 2 in parallel or you can solder directly to the terminals but a very hot Iron is needed to make the join quickly, too slow and the cell will be damaged.

Thanks Dave,
That is JUST the information I was looking for and could not find. That will make it as close to original (and working) as you can get.
doug