My first bikes were all James models. I'm pretty sure the model you are referring to was a Commander not commando.
I had 1x 1957 James comet which was a 98cc semiauto 2speed 2stroke and 2x James captains (1951&1953 i think) both fitted with 197cc 2stroke villiers 3 speeds.
I believe the commander was the 250cc model but can't be sure as it was pre Internet popularity times. To get parts and info I had to either ding lawn mowers at garage sales and get ignition parts or find old timers who were interested in sharing or helping a young fella out. My captains were both plunger models.
Your search engine was just bikes magazine, looking for ads for old bsa bantam stuff and heaps of phone calls to see if the guy on the end of the line could help you or at least point you in the right direction.