I believe the Cycle electric generator is available for sport scouts/741 also. Ask the indian parts dealers.
You could use a VW generator. Or a 12 volt bosch generator from the '60s like we use here.
The rotation needs to be changed (at least on the 12v), switch the connections on the field.
The 12volt bosch needs the generator housing turned down on a lathe, since it has a slightly larger diameter than the indian generator clamp.
A ready to install indian bosch 12volt generator with electronic regulator is available from Sweden, this looks just like an autolite. I have one of those on my chief. I run a toothed belt(with a different ratio) on mine, makes it start charging much earlier.
There are some tiny Japanese alternators on the market.
I wonder if a such could be hidden inside a tube with an autolite endcover.
1944 Indian Chief + sidecar
1939/40 Sport scout bobber,