Something like this:
But this is not really balance charging, it’s just individual termination and bypass when one of the cells is fully charged (isn’t it?).
So you have to continue charging until both cells are fully charged.
I think you also need a current limited input.
It’s probably not advised to let the BMS limit the charging current.
That’s only a protection feature, not intended to regulate your charging current.
So, what you would need with this kind of BSM is some boost circuit (5 Volts to 8.5 Volts) with a constant current output.
I guess you could use a LED boost driver for that?
There’s always very little information in those listings…